Pre-Stressed Modular Retaining Wall System and Method

ABSTRACT

The present invention relates to a system and method for constructing a pre-stressed modular construction for supporting or retaining an applied load. In particular, the present invention relates to a system and method for pre-stressed modular retaining walls. The system comprises a plurality of header stacks constructed from a variety of header units. The header stacks are coupled by structural members. Active reinforcement elements are used to induce a pre-stressing force into the header stacks to support or retain the applied load. A method for constructing the modular construction is provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a system and method for fabricating apre-stressed modular construction for supporting or retaining an appliedload. More particularly, the present invention relates to a system andmethod for pre-stressed modular retaining walls.

2. Related Art

A retaining wall is an engineered structure that has the particular taskof ensuring that a given unstable, or potentially unstable, soil mass isprevented from moving under the influence of gravity. Frequently, theretaining wall is also called upon to withstand a superimposed load, asurcharge load, on and/or within the soil mass, such as a highway,together with its traffic loading, or the loading induced by thefoundations of a building located in close proximity to the retainingstructure. Further, the retaining wall may be required to support someother non-retaining load that is resisted by structural elementsdirectly attached to, and/or incorporated within, the wall structureitself.

Since the early 1970's, numerous alternative wall systems have beenintroduced. Examples of these systems include mechanically stabilizedearth (MSE) walls and reinforced soil slopes (RSS) employing metallic orpolymeric internal reinforcement; anchored walls, such as the soldierpile and lagging walls, diaphragm walls, and soil mixed walls;prefabricated modular gravity wall systems including cribs, bins, andgabions; and in-situ reinforced wall systems such as soil-nailed wallsand micropile walls. However, because of the ever increasing demandsthat are being placed on our city and urban environments and, mostnoticeably, on the country's transportation infrastructure, togetherwith the need to preserve our natural environment while providing forthe associated societal expectations, there is an increasing number ofproblematic sites where the currently available retaining wall optionscannot provide an optimal solution. In particular, for those sites thatrequire “foundation-up” construction, there is a dearth of rapidconstruct, high capacity retaining wall systems possessing significantfunctional flexibility and which demand only a small constructionfootprint. Retaining structures constructed to resist soil pressures areoften categorized according to their basic mechanisms of retention. Theretention mechanisms include internally stabilized, externallystabilized, and hybrid systems. Alternatively, retaining walls may becategorized according to their source of support, that is, their sourceof equilibrating reaction forces. The sources of support for theseretaining walls may be bracketed into gravity, semigravity, andnongravity.

An internally stabilized system involves reinforced soils to retain asoil mass and any surcharge loads. This reinforcing may be provided byadding reinforcement directly to the soil mass, where this augmentedsoil mass is providing the retaining/self-retaining structure, as thesystem is being constructed from the “ground” up. Various types ofreinforcement are available, and the soils between the layers ofreinforcement are placed in a carefully controlled manner meeting designspecifications—that is, the placed soil is “engineered fill.”Frequently, pre-cast concrete elements are tied directly to these soilreinforcing components. This system forms the basic approach ofMechanically Stabilized Earth, MSE, retaining wall systems.

Alternatively, this internal stabilization via the reinforcing of thesoil mass in question may proceed from the top down. In this(directionally) opposite approach, reinforcing elements are added to theexisting soil mass in order to provide the existing materials with agreater degree of internal stability. As an example of this approach,the face, that is exposed as the excavation proceeds from the top down,has soil nails installed through it into the ground mass, which nailsextend beyond any potential failure plane. Often, a shotcrete cover overthe exposed face is placed and subsequently connected to these nails,thereby providing a protection against erosion of the soil face.

Further to the above methods of reinforcing a soil mass, driven piles orcast-in-drilled-hole piles may be used to stabilize the mass of concern.However, this approach is generally considered when the stability issueis more global in nature. By “global” is meant the situation where abody of soil is experiencing a deep-seated instability, whichinstability ideally needs to be eliminated.

With externally stabilized systems, a physical structure is employed toconfine the body of soil. The equilibrating reaction forces, required byan externally stabilized system, are provided either through the weightof a morpho-stable structure, or by the reactions mobilized via theinclusion and/or extension of various system elements into “reactionzones”. The latter reactions may be generated by driving the piles of asheet-pile wall system, for example, to sufficient depths into competentsoil. Or, reactions may be generated via the use of ground anchorsproviding point-reactions on the externally stabilizing structure.Frequently, combinations of reaction-force-providing structural elementsare employed, in a given situation, to deliver the total forceequilibration required for an externally stabilized retaining wall.

With regard to sources of support, that is, with regard to the sourcesof the equilibrating reaction forces, retaining wall systems may becategorized into three groups. These are the groupings of (1) gravitywalls, (2) semigravity walls, and (3) nongravity walls.

Gravity walls derive their capacity to resist imposed soil loads throughthe dead weight of the wall itself (that is the physical wall that isconstructed) or through an integrated mass that can be either internallyor externally stabilized. Gravity walls may be further classified intofour types as follows. The first type is an internally stabilized soilmass system. Some of the examples given above are typical. The stabilityof a cut slope may be maintained in a top-to-bottom installation of soilnails, installed as the excavation of materials proceeds. Or, aretaining soil mass may be constructed of engineered fill, in abottom-to-top sequence, thereby creating a soil mass possessing therequired internal stability via the inclusion of reinforcing elements atregular vertical spacing. Where the soil mass is constructed fromengineered fill, the face of such soil mass may be protected by usingpre-cast concrete facings as with many MSE systems. Where soil nails areused, the front face is preferably protected using shotcrete orcast-in-place concrete. The second type of gravity wall is an externallystabilized soil mass system. Included in this category are simplemodular pre-cast concrete walls. Such simple pre-cast concrete walls arestacked, but include no internal mechanism for enhancing structuralcapacity. Another example is prefabricated metal bin walls. The thirdtype is also an externally stabilizing system. In this category are thegeneric walls including the masonry walls, the stone walls, “dumped”(usually shaped) rock walls, and the contained rock walls, often usinguniform crushed rock and known as gabion walls. The fourth system isalso an externally stabilizing system. Examples are the use ofcast-in-place mass concrete wall, or the cement-treated soil wall. Wherethe face of the treated soil wall requires protection, a pre-castconcrete panel may be used, which panel would be anchored to thetreated-soil wall.

Semigravity walls derive their restraining capability through thecombination of dead weight and structural resistance. Generally, thesesemigravity walls are externally stabilizing structures. They may beconstructed on spread footings or on deep foundations. Historically, thedominant type of semigravity retaining wall is the conventionalcast-in-place concrete cantilever structure. Alternatively, variouskinds of pre-cast concrete walls are available in the market, whichwalls are constructed on cast-in-place footings. Cantilever semi-gravityretaining walls may be very reliant on the dead weight of the soil massthat rests on the section of the foundation footing that extends backbeyond the wall's stem, while also developing the necessary structuralresistance. An example of the necessary structural resistance would bethe wall's moment and shear capacity at the base of the stern.

Nongravity walls derive their restraining capability through lateralresistance. This lateral resistance may be mobilized in a number ofways. For example, the continuation of vertical structural elements downto competent soils, or the use of ground anchor retainers directlydelivering point resistance to the retaining structure. Examples ofexternally stabilizing nongravity systems are embedded cantileveringwall elements, sheet piles, drilled shafts, or slurry walls. A secondgroup of nongravity walls includes the first listing of embedded wallsbut have additional restraint via utilizing multiple ground anchorretainers.

Where, for example, there is a need to arrest the creep movement of aslope, nongravity systems may be employed in the form of dowel piles orcaissons, to internally stabilize the soil mass. It should be noted thatrequired equilibrating forces may be developed via the use of reactionmembers which develop point-reaction-forces. (Consider the reactions toa truss, which truss transfers moment to its support). That is, thestructural elements delivering resistance to the retaining wallstructure overall may have so little moment (and shear) resistingcapacity, if any, that the equilibrating set of forces are establishedvia point-acting reaction forces. For example, an arrangement ofelements for such a system, may consist of a set of vertical (or nearvertical) piles, a set of (near) vertical ground anchors and, finally, aset of (near) horizontal ground anchors. In this case, the piles wouldtake up compression loads, the (near) vertical ground anchors wouldprovide a (predominantly) downward reaction, which would act in concertwith the piles' upward reaction to provide moment resistance to the basefoundation. The (near) horizontal ground anchors, placed appropriatelyat the foundation beam/pile cap level, would resist the net “shear”forces from the retaining wall structure that would cause the foundationelement to translate.

An example of a retaining wall is shown, for example, in U.S. Pat. No.2,149,957 (“the Dawson patent”). The wall of the Dawson patent utilizesstretchers and headers to construct a retaining wall. Dawson furtherdiscloses “positive tensile anchorage.” Such “positive tensileanchorage” refers to the construction of the individual elements and hasno impact on the primary behavior of the system disclosed in the Dawsonpatent. Moreover, the wall of the Dawson patent does not pre-stressheader assemblies through post-tensioning. Further, the Dawson patentdoes not disclose vertically disposed passive reinforcement through theheader assemblies.

Retaining wall systems, such as those shown in the Dawson patent, oftendo not provide an optimal solution for retaining or supporting anapplied load. The design of conventional retaining wall systems mayresult in constructibility problems, resulting in longer constructionperiods, higher cost, and more extensive use of the surrounding land.Thus there is a need in the art for a retaining wall system thatprovides an improved solution for retaining or supporting an appliedload and overcomes the limitations of constructibility problems withexisting systems. There is a further need in the art for a retainingwall system that is modular and adaptable to a wide variety ofconstruction needs.

SUMMARY OF THE INVENTION

The present invention solves the problems with, and overcomes thedisadvantages of conventional retaining wall systems. Accordingly, thepresent invention provides a system and method for constructing apre-stressed modular construction for supporting or retaining an appliedload. The retaining wall systems of the present invention arespecifically designed to provide the owner, architect, engineer, andconstructor with retaining wall solutions that most adequately providefor more difficult sites and/or increased performance expectations.

The present invention relates to a system and method for constructing apre-stressed modular construction for supporting or retaining an appliedload. In particular, the present invention relates to a system andmethod for constructing pre-stressed modular retaining walls. In oneaspect of the present invention, a system for constructing apre-stressed modular construction for retaining or supporting an appliedload is provided. The system comprises a header stack, wherein theheader stack is comprised of a plurality of header units; and an activereinforcement element configured to cooperate with the header stack sothat post-tensioning the active reinforcement element imparts acorresponding pre-stressing force into the header stack. In oneembodiment of the invention, the header units that make up the headerstack comprise a center element having a top face, and a bottom face; afirst end element disposed at one end of said center element; and asecond end element disposed at another end of said center element.

The system may comprise active reinforcement elements disposed externalto the header stack. In such a configuration, there may be passivereinforcement elements disposed internal to the header stack.Additionally, active reinforcement elements may be disposed internal tothe header stack.

In another aspect of the system, the header units that make up theheader stack comprise a top face and a bottom face; a base elementhaving a first end and a second end; a head element having a first endand a second end; and a pair of side elements extending between each ofthe first end and the second end of the base element and the headelement. The system further comprises a structural member for couplingtwo or more header stacks and a complementary structural elementdisposed between two header units and extending between two or moreheader stacks.

In another aspect of the invention, a pre-stressed modular constructionfor retaining or supporting an applied load is provided. Theconstruction comprises a plurality of header stacks, wherein each of theheader stacks comprises a plurality of header units; and a plurality ofactive reinforcement elements configured to cooperate with at least oneof the header stacks so that post-tensioning the active reinforcementelement imparts a corresponding pre-stressing force into the headerstack. There are a plurality of structural members, wherein each of thestructural members is coupled to at least one of the header stacks. Inan exemplary embodiment of the construction, the header units that makeup the header stack comprise a center element having a top face, and abottom face; a first end element disposed at one end of the centerelement; and a second end element disposed at another end of the centerelement.

In another aspect of the pre-stressed modular construction, the headerunits that make up the header stack comprise a top face and a bottomface; a base element having a first end and a second end; a head elementhaving a first end and a second end; and a pair of side elementsextending between each of the first end and the second end of the baseelement and the head element. The construction further comprises astructural member for coupling two or more header stacks and acomplementary structural element disposed between two header units andextending between two or more header stacks.

In a further aspect of the invention, a pre-stressed modularconstruction for retaining or supporting an applied load is provided.The pre-stressed modular construction preferably comprises at least twoheader stacks, each of the header stacks being comprised of a pluralityof stacked header units. There is also preferably at least onepre-stressing tendon for each of the header stacks, with eachpre-stressing tendon being configured to cooperate with its header stackso that post-tensioning the pre-stressing tendon prior to application ofthe applied load imparts a corresponding pre-stressing force into itsheader stack at least one lock-off point. There is also a structuralmember coupled to the at least two header stacks. The pre-stressedmodular construction further preferably comprises a tieback transferbeam disposed between two of the header units and extends between the atleast two header stacks. There is also a ground anchor coupled to thetieback transfer beam. The structural member can be a concretestretcher, a pre-cast concrete panel, a cast-in-place concrete panel, acast-in-place concrete arch, or shotcrete.

In another aspect of the invention, a method of fabricating apre-stressed modular construction for retaining or supporting an appliedload is provided. The method comprises providing a foundation for theconstruction; constructing a plurality of header stacks on thefoundation, with each header stack being comprised of a plurality ofheader units; coupling an active reinforcement element to each headerstack; and post-tensioning the active reinforcement element such that itimparts a corresponding pre-stressing force into the header stack. Theconstructing step comprises stacking a plurality of header units. Thecoupling step comprises pre-positioning the active reinforcement elementin the foundation; feeding the header units over the activereinforcement element, the active reinforcement element passing throughpassthrough ducts in the header units; and securing the activereinforcement element to the header stack. In a configuration whereexternal active reinforcement elements are used, the activereinforcement elements may be locked off in a variety of ways. Theactive reinforcement elements may be locked off at external couplingdevices coupled to the header stack, or locked off at a complementarystructural element.

In a further aspect of the invention, a method of fabricating apre-stressed modular construction for retaining or supporting an appliedload is provided comprising the steps of suspending a plurality ofheader units; casting a foundation beneath the header units;constructing a plurality of header stacks on the cast foundation,wherein each header stack is adjacent one of the plurality of suspendedheader units; coupling an active reinforcement element to the headerstack; and post-tensioning the active reinforcement element such that itimparts a corresponding pre-stressing force into the header stack.

In a further aspect of the present invention, a method of fabricating apre-stressed modular construction for retaining or supporting an appliedload is provided. The method comprises the steps of providing afoundation for the construction; constructing a plurality of headerstacks on the foundation, wherein each header stack comprises aplurality of header units; coupling an active reinforcement element toeach header stack, post-tensioning the active reinforcement element suchthat it imparts a corresponding pre-stressing force into at least one ofthe header stacks; providing additional header units to at least one ofthe header stacks; and repeating the step of post-tensioning afterapplication of another portion of the applied load. In a still furtheraspect of the present invention, a method of fabricating a pre-stressedmodular construction for retaining or supporting an applied load isprovided. The method comprises the steps of providing a foundation forthe construction; constructing a plurality of header stacks on thefoundation, wherein each header stack comprises a plurality of headerunits; coupling an active reinforcement element to each header stack;imparting a portion of the applied load to the modular construction;post-tensioning the active reinforcement element such that it imparts acorresponding pre-stressing force into at least one of the headerstacks; providing additional header units to at least one of the headerstacks; and repeating the step of post-tensioning after application ofanother portion of the applied load.

Features and Advantages

An advantage of the present system is that structural pre-stressing maybe sequentially modified, most typically increased, as the soil loadingon the retaining wall changes.

Another advantage of the present system is that retaining wall(vertical) sections may be given sufficient and/or final pre-stress soas to allow for the construction of other structural members. Ifnecessary, this could all take place before the soil loads are placed onthe wall.

A further advantage of the present system is that the retaining wallstructure may be stressed so as to always possess “residual”, or “net”,compressive stress on the “tension” side of any given header stackcross-section. This latter characteristic would be called on inenvironmentally hostile situations. For example, environmentally hostilesituations may exist where naturally aggressive minerals are present inthe ground water in contact with, or in close proximity to, theretaining wall, or where the retaining wall is a sea wall.

An advantage of the system of the present invention is readyavailability. Short period cyclic casting of standardized structuralmodules assures that structural components are produced in sufficientquantities to satisfy fast track construction schedules.

A further advantage of the system of the present invention is superiorquality control. Plant-cast pre-cast concrete components aremanufactured under optimum conditions of forming, fabrication andplacement of the reinforcement, inclusion of pre-stressing passthroughducts and other embedded items and features. The optimally controlledplacement and compaction of low slump concrete having optimized mixdesign and control, along with favorable curing conditions, typicallynot achievable on site, further significantly increase the in-serviceperformance of these elements.

Yet another advantage of the system of the present invention, forretaining wall construction possessing a given structural capacity, isreduced construction depth. High performance concrete is easilyachievable. For any given loading conditions, via the correct selectionof (sub)group of components, the retaining structure depth may beminimized, a significant advantage where space is at a premium.

Another advantage of the system of the present invention is its highload-resisting capacity. For a given set of spatial restrictions and/orfor a given volume of materials used, pre-cast pre-stressed concreteoffers greater structural strength and rigidity. These attributes becomevery significant in many applications.

A further advantage of the system of the present invention is itsdurability. Pre-cast concrete, in particular high-performance pre-castconcrete, is exceptionally resistant to weathering, abrasion, impact andcorrosion. The resulting structures have great resistance to thedeleterious effects found in hostile environments.

Yet another advantage of the system of the present invention is its longeconomic life. The reliability of currently available pre-stressingsystems and the durability characteristics of the pre-cast elementsallow for the economic construction of very-long-life retaining and/orsupport structures. Pre-stressing reduces or, if required, completelyeliminates tension cracks, and thereby guarantees the integrity of theconcrete and the protection of the embedded steel elements.

Another advantage of the system of the present invention is derived fromthe use of architectural concrete. The process of pre-casting concretecomponents, for example, the pre-cast panels that may be used withcertain embodiments of the present invention, tends itself to thesculpturing of these exposed elements, and the consequent enhancedappearance of the final structure.

Still another advantage of the system of the present invention is theflexibility of construction sequence. The application of pre-stress, inparticular the staged and/or sequenced application of pre-stress, to theassemblies of pre-cast concrete modules in these systems allows forsequenced construction without re-setup penalties.

Another advantage of the system of the present invention is the controlof shrinkage and creep, and the consequent effects of same, whichcontrol can essentially be “dialed up.” In this regard, the readyquality control of concrete products, that are manufactured viaplant-cast pre-casting, affords greater accuracy in the determination ofanticipated shrinkage and creep. With knowledge of the characteristicsof pre-stressing components and the concrete characteristics of thevarious modules, along with the control of the pre-stressing stressmagnitudes and distributions, the shrinkage and creep may be accuratelypredetermined.

Another advantage of the system of the present invention is thereduction or complete elimination of site formwork. Certain embodimentsof the invention, as built above foundation level, are constructedentirely independent of cast-in-place concrete.

A further advantage of the present invention is its speed ofconstruction. The fact that all embodiments can employ pre-cast headermodules, used to form the header stacks, and some can be completelycomprised of pre-cast elements, contributes significantly to theguaranteed speed of erection. One of the principal aims of these systemsis to provide retaining wall and/or support structural systems that, notonly provide high capacity, but may be erected with great rapidity.

Additional features and advantages of the invention will be set forth inthe description that follows, and in part will be apparent from thedescription, or may be learned in practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with the description, serve to explain the features,advantages, and principles of the invention.

FIG. 1 is a perspective view of an exemplary system according to thepresent invention.

FIG. 2 is a perspective view of an alternative exemplary embodiment ofthe system according to the present invention.

FIG. 3 is an exploded perspective view of an alternative embodiment ofthe system according to the present invention.

FIG. 4 is an exploded perspective view of an alternative embodiment ofthe system according to the present invention.

FIG. 5 is a perspective view of an alternative exemplary embodiment ofthe system according to the present invention.

FIG. 6 a is a plan view of an exemplary embodiment of a header accordingto the present invention.

FIG. 6 b is a plan view of an alternative exemplary embodiment of aheader according to the present invention.

FIG. 6 c is a plan view of an alternative exemplary embodiment of aheader according to the present invention.

FIG. 6 d is a plan view of an alternative exemplary embodiment of aheader according to the present invention.

FIG. 6 e is a side view of an exemplary embodiment of a header accordingto the present invention.

FIG. 7 a is a perspective view of an alternative exemplary embodiment ofa header according to the present invention.

FIG. 7 b is a top plan view of the exemplary header in FIG. 7 a.

FIG. 7 c is a side elevation of the exemplary header in FIGS. 7 a and 7b.

FIG. 8 is a perspective view of one embodiment of a modular constructionaccording to the present invention.

FIG. 9 is a perspective view of an alternative embodiment of a modularconstruction according to the present invention.

FIG. 10 is a perspective view of an alternative embodiment of a modularconstruction according to the present invention.

FIG. 11 is a perspective view of an alternative embodiment of a modularconstruction according to the present invention including acomplementary structural element.

FIG. 12 is a perspective view of an alternative embodiment of a modularconstruction according to the present invention including cast-in-placeconcrete panels.

FIG. 13 is a perspective view of an alternative embodiment of a modularconstruction according to the present invention.

FIG. 14 a is a perspective view of a partial modular constructionaccording to the present invention.

FIG. 14 b is a perspective view of an exemplary header in a partialmodular construction according to the present invention.

FIG. 15 a is a perspective view of an exemplary header in a partialmodular construction according to the present invention.

FIG. 15 b is a perspective view of an exemplary header in a partialmodular construction according to the present invention.

FIG. 16 is a perspective view of an alternative exemplary embodiment ofthe system according to the present invention including exemplary activeand passive reinforcement elements.

FIG. 17 is a detailed perspective view of a lock-off element accordingto the present invention.

FIG. 18 is a perspective view of an alternative exemplary embodiment ofthe system according to the present invention including exemplary activeand passive reinforcement elements.

FIG. 19 is a perspective view of an alternative exemplary embodiment ofthe system according to the present invention including exemplary activeand passive reinforcement elements and harping elements.

FIG. 20 is a detailed view of an exemplary harping element of FIG. 19.

FIG. 21 a is a side elevation of an exemplary embodiment of a headeraccording to the present invention.

FIG. 21 b is a perspective view of the header in FIG. 21 a

FIG. 21 c is a side elevation of an alternative exemplary embodiment ofa header according to the present invention.

FIG. 21 d is a perspective view of the header in FIG. 21 c.

FIG. 22 is a perspective view of a partial modular constructionemploying the exemplary headers in FIGS. 21 a, 21 b, 21 c, and 21 d.

FIG. 23 is a perspective view of a modular construction employing theexemplary headers in FIGS. 21 a, 21 b, 21 c, and 21 d.

FIG. 24 a is a perspective view of an exemplary modular constructionaccording to the present invention depicting the use of corner stacks.

FIG. 24 b is a detailed view of an exemplary corner closure unitaccording to the present invention.

FIG. 24 c is a detailed view of an alternative exemplary corner closureunit according to the present invention.

FIG. 24 d is a top plan view of the modular construction in FIG. 24 aand employing the corner closure units in FIGS. 24 b and 24 c.

FIG. 25 a is a perspective view of an exemplary modular constructionaccording to the present invention depicting the use of an alternativeembodiment of corner stacks.

FIG. 25 b is a detailed view of an alternative exemplary corner closureunit according to the present invention.

FIG. 25 c is a detailed view of an alternative exemplary corner closureunit according to the present invention.

FIG. 25 d is a top plan view of the modular construction in FIG. 25 aand employing the corner closure units in FIGS. 25 b and 25 c.

FIG. 26 a is a top plan view of an alternative embodiment of a modularconstruction according to the present invention employing corner stacks.

FIG. 26 b is a perspective view of the modular construction of FIG. 26 a

FIG. 27 a is a top plan view of an exemplary header unit according tothe present invention.

FIG. 27 b is a perspective view of the header unit of FIG. 27 a

FIG. 27 c is a top plan view of an exemplary header unit according tothe present invention.

FIG. 27 d is a top plan view of an exemplary header unit according tothe present invention.

FIG. 27 e is a top plan view of an exemplary header unit according tothe present invention.

FIG. 27 f is a top plan view of an exemplary header unit according tothe present invention.

FIG. 27 g is a top plan view of an exemplary header unit according tothe present invention.

FIG. 27 h is a top plan view of an exemplary header unit according tothe present invention.

FIG. 27 i is a side view of an exemplary embodiment of a headeraccording to the present invention.

FIG. 28 is a perspective partial view of a modular constructionaccording to the present invention and employing the header of FIGS. 27a and 27 b.

FIG. 29 is a perspective partial view of an alternative embodiment of amodular construction according to the present invention and employingthe header of FIGS. 27 a and 27 b and depicting exemplary activereinforcement elements.

FIG. 30 is a perspective partial view of an alternative embodiment of amodular construction according to the present invention and employingthe header of FIGS. 27 a and 27 b and depicting exemplary activereinforcement elements.

FIG. 31 is a perspective partial view of an alternative embodiment of amodular construction according to the present invention and employingthe header of FIGS. 27 a and 27 b and depicting exemplary activereinforcement elements.

FIG. 32 is a perspective partial view of an alternative embodiment of amodular construction according to the present invention and employingthe header of FIGS. 27 a and 27 b and depicting exemplary activereinforcement elements and passive reinforcement elements.

FIG. 33 is a perspective partial view of an alternative embodiment of amodular construction according to the present invention and employingthe header of FIGS. 27 a and 27 b.

FIG. 34 a is a side elevation of an exemplary application of the systemof the present invention.

FIG. 34 b is a cross section of an exemplary application of the systemof the present invention depicted in FIG. 34 f.

FIG. 34 c is a side elevation of an exemplary application of the systemof the present invention.

FIG. 34 d is a side elevation of an exemplary application of the systemof the present invention.

FIG. 34 e is a side elevation of an exemplary application of the systemof the present invention.

FIG. 34 f is a perspective view of an exemplary application of thesystem of the present invention.

FIG. 34 g is a perspective view of an exemplary application of thesystem of the present invention.

FIG. 34 h is an enlarged perspective view of a portion of the system ofFIG. 34 g.

FIG. 34 i is a perspective view of an exemplary application of thesystem of the present invention.

FIG. 34 j is a perspective view of an exemplary application of thesystem of the present invention.

FIG. 34 k is a front elevation of an exemplary application of the systemof the present invention.

FIG. 34 l is a perspective view of the application in FIG. 34 k.

FIG. 34 m is a perspective view of an exemplary application of thesystem of the present invention.

FIG. 34 n is an enlarged perspective view of a portion of the system ofFIG. 34 m

FIG. 34 o is a front elevation of an exemplary application of the systemof the present invention.

FIG. 34 p is a cross section of the application of FIG. 34 o along theline p-p.

FIG. 34 q is a cross section of the application of FIG. 34 o along theline q-q.

FIG. 34 r is a perspective view of an exemplary application of thesystem of the present invention.

The illustrations shown herein, of necessity, take presentationliberties. Among these are the sectioning of the retaining wallstructures. In order to show close-up detail only small sections of theoverall structure are shown. Moreover, only some of the figures indicatethe sectioned nature of the components via the use of exposedreinforcing steel. Additionally, for example, the shear reinforcingsteel may be omitted, where any rebar is indicated at all. Generally,the soil/rock mass being retained by any given retaining wall is notindicated in these figures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. The exemplary embodiments of this invention areshown in some detail, although it will be apparent to those skilled inthe relevant art that some features may not be shown for the sake ofclarity.

The systems of the present invention possess fundamental characteristicsthat are common to all of the constituent groups (i.e. subsystems). Thesystems are preferably comprised, at least partially, of pre-castconcrete components, called headers 110 or header units 110. Thesecomponents, when stacked one on top of the other, form header stacks101. These header stacks 101 are then augmented in a variety of ways.The augmenting members generally form secondary structural members 130.These components are secondary in the sense that they are available toresist soil loading, directly transferring these loads to the primarystructural members, the header stacks 101, which transfer theaccumulated loads to structural elements which elements mobilize theequilibrating reaction forces which will be explained in detail below.These secondary structural members 130, or structural members, may becomprised of pre-cast concrete “stretchers”, pre-cast concrete panels,cast-in-place (CIP) concrete panels, cast-in-place (CIP) concretearches, or may be constructed from various configurations of shotcrete.

Another characteristic of the present invention that is consistentthroughout these systems, is the manner in which the header stacks 101are imparted their structural capacity to withstand imposed or appliedload. The pre-cast concrete header units 110 that are stacked in avertical plane, are, at predetermined stages of the constructionprocess, pre-stressed. This pre-stressing is typically imparted to theheader stacks 101 via the post-tensioning of tendons 115, which include,but are not limited to, cables, rods, or threadbars.

Another element of the system is a complementary structural element 1100(best seen, for example, in FIGS. 11 and 13), which may be referred toherein as a tieback transfer beam (or TTB). This complementarystructural element 1100 may have more than one role. In one principalrole, the complementary structural element 1100 will “gather”, primarilythe lateral components of, the accumulated loads being resisted by theheader stacks 101, and transfer them to the equilibrating reactionforces that are provided by other structural elements, such as tiebacks.The complementary structural element 1100 may also be used to couple aretaining wall horizontally. This would have particular applicabilitywith non-composite systems, that is, systems that do not have transversereinforcement elements formed in, or passing through, the header unit110. For example, the systems employing secondary structural members ofarching shotcrete between header stacks 101, or where the secondarystructural members are pre-cast panels. Further, the complementarystructural elements 1100 may be used in other ways. If, for example,there existed a need to apply additional restraint to a limited area ofthe retaining wall, a complementary structural element 1100 could beincluded in that area, and so used to provide the necessary reaction(s).Also, these complementary structural elements 1100 may be used togetherwith foundation beams, as continuous elements. This would apply, forexample, where the base of the wall was being stepped-up. For example,this would apply where the retaining wall being constructed had aU-shaped frontal elevation. The complementary structural element 1100may also be used to couple various intersecting retaining wall sections.The complementary structural element 1100 may also be used to supportother structural members which members are framing into the wall/supportstructure and which members are employed to resist non-soil-retentionloads (for example, as is illustrated in FIGS. 34 c, 34 d, and 34 e).

As part of any structure fabricated in accordance with the presentinvention, header stacks 101 are always present. These header stacks 101are preferably formed from pre-cast concrete elements, called headers110. The headers 110 are preferably vertically stacked, or preferablystacked in a vertical plane. Alternatively, the headers 110 may berotated such that they are aligned in a horizontal plane. The secondarystructural members 130 and the complementary structural elements 1100may be formed from different materials. Further, the secondarystructural members 130 may be positioned either at the front of thestructure or at the rear of the structure or at both the front and therear of the structure. The rear of the structure refers to the face ofthe wall that contacts the soils 34 (seen in FIGS. 34 a, 34 c, 34 d, 34e, 34 g, 34 p, 34 q, and 34 r) being retained by it. The front of thestructure refers to the face of the wall that does not contact the soilor other retained load. Note also that the secondary structural members130 and complementary structural elements 1100 that may be chosen forthese walls may interact with the header stacks 101 in various ways. Inthis respect, there is significant flexibility available to thedesigner, via the most appropriate selection of a systems group to beinstalled at a given location.

As used herein, the term “pre-stressing” refers to the process ofimparting beneficial stress profiles, to the structure, to thestructural member, or structural component, most typically prior to thestructure, structural member or component, being subjected to theanticipated, externally applied loads. The process may involve sequencedsets of discrete pre-stressing stages.

As used herein, the term “reinforcement” refers to either “passivereinforcement” or to “active reinforcement”. Any particular zone orcross-section within the various structural members that comprise thesesystems, or any components that comprise such members, may beunreinforced, or possess passive reinforcement, or active reinforcement,or both passive and active reinforcement, depending on the location ofthe zone or cross-section within the structural system and thestructural performance expectations of same.

As used herein, the term “passive reinforcement” refers to reinforcementthat is in a neutral state of stress prior to the associated componentor member being subjected to applied forces. Where included inreinforced concrete members, a passive reinforcement element istypically referred to as non-pre-stressed reinforcement. The appliedforces, that are referred to here, may be induced by body forces, byexternally imposed loads acting directly or indirectly on a component ormember, or be the result of axial forces that are imposed on apre-stressed concrete member by pre-stressing forces (typically) priorto the application of external loads. One way to view passivereinforcement is to recognize that it is any reinforcement, includedwithin the member or component, that has not been tensioned specificallyto generate a favorable stress regime within the concrete of thestructural member or component typically prior to that member orcomponent being subjected to the body forces and external loads that itis intended to sustain.

As used herein, the term “active reinforcement” refers to reinforcementthat has been subjected to positive tensile force(s), thereby inducingtherein a state of positive (tensile) stress, typically prior to theassociated member or component being subjected to body forces and theanticipated externally applied loads. As used herein, the term “activereinforcement element” refers to any reinforcement element (positionedwithin the structural component, member, or system and) intended for thestructural role of providing and maintaining a pre-stressing force inthe structural component or member or in a structural assembly comprisedof the same. In accordance with the present invention, this may be doneby the jacking of predetermined tensile force(s) into activereinforcement element 115 typically prior to the structural member sostressed being subject to externally applied loads. Active reinforcementelement 115 may include, but is not limited to, a wire, a strand, acable, a rod, or other suitable element specifically designed for thestructural role of providing and maintaining a pre-stressing force inthe structural component or member or in the assembly composed of same.The active reinforcement element 115 is placed in a state of positive,tensile stress through a process of post-tensioning. Activereinforcement elements may be placed in a state of positive, tensilestress through a process of pre-tensioning. Such pre-tensioned activereinforcement elements may be used in such structural components ormembers as the stretchers 130, and the appurtenant structural elementssuch as element 3450 as shown in FIGS. 34 a, 34 b and 34 f, for example.

As used herein, the term “pre-tensioning” refers to the process wherebypredetermined tension forces are imparted into the pre-stressing activereinforcement element(s), before the concrete of the component or memberis placed in the forming molds about the active reinforcement element(s)and, if included, passive reinforcement elements. After the concrete hasgained the necessary strength to withstand the stresses that will beinduced at transfer, the pre-stressing forces that were imparted intothe active reinforcement elements are released from the pre-tensioningdevice, and thereby these forces are transferred to, and resisted by,the concrete of the component or member being pre-stressed, and thepassive reinforcement elements, if included. The high-strength tendonsthat may form active reinforcement elements normally take the form ofwire, or strand. These tendons possess high performance stress-straincharacteristics. In the process of pre-tensioned pre-stressing, wheresteps are not taken to prevent bond, the active reinforcement elementsare typically bonded to the surrounding concrete.

As used herein, “post-tensioning” is the process whereby tension forcesare imparted into the active reinforcement elements 115 after thepre-cast concrete components or members have been manufactured and,generally, have been placed in their final position within thestructural assembly. The post-tensioning process is also frequently usedto pre-stress active reinforcement elements 115 that are used inconjunction with cast-in-place concrete. In either case, where internalpre-stressing tendons are being used, the process requires the provisionof suitable ducting to correctly locate the tendons to be stressed. Inthe case of cast-in-place (CIP) concrete components or members, theinternal active reinforcement elements 115 may be placed in the ductsbefore the concrete is situated or may be fed through the ducts afterthe concrete has cured sufficiently. In the case where internal activereinforcement elements 115 are being used in conjunction with structuralelements or members that are comprised of pre-cast concrete components,for example, pre-cast concrete headers 110, the “duct” is formed by thesuccessively abutting passthrough ducts 116 that comprise a feature ofeach header unit 110. In the case of external pre-stressing tendons theactive reinforcement elements 115 generally do not require such ducting.The exceptions are where such external active reinforcement elements 115pass through complementary structural elements 1100, such as tiebacktransfer beam 1100, or capping beams, or where these external activereinforcement elements 115 are anchored within a foundation element1450, 500 and/or are being locked of at a tieback transfer beam, acapping beam, or other complementary structural element 1100. In markedcontrast to the process of pre-tensioning, and the transfer ofpre-stressing force associated with the process of pre-tensioning, theforces that are placed in the active reinforcement elements 115 duringthe process of post-tensioning are preferably transferred to thestructural component, or member, or complementary element, or foundationelement, or structural assembly composed of same at reaction and/orlock-off points only. The pre-stressing forces placed in the activereinforcement elements 115 must be sustained by the structural componentor member or complementary element, or foundation element, or structuralassembly composed of same at two transfer points. The internal activereinforcement elements 115 may be fully bonded to the associated ductsor left unbonded. The bonding of the active reinforcement elements 115to the ducts, which ducts are already bonded to the surroundingconcrete, which was cast in place, where cast-in-place concrete is beingused is normally achieved by grouting. Such cast-in-place (CIP) concretemay be found in the foundation elements, the TTBs, and the cappingbeams. Further, such CIP concrete may also be found in the secondarystructural elements that are disposed between the header stacks. Wherepassthrough ducts 116 are formed in the concrete of the pre-castcomponents or members, for example, the header units 110, where abuttingfeatures 116 of successive header units 110 form the ducts associatedwith an active reinforcement element 115, via grouting of the activereinforcement elements 115 to the ducts so formed, bonding is achieveddirectly to the concrete of these pre-cast units.

Referring now to FIGS. 1 through 5, there is illustrated an exemplaryembodiment of the system of the present invention. In the embodimentdepicted in FIGS. 1-5, system 100 for constructing a pre-stressedmodular construction for retaining or supporting an applied load isdepicted. It should be understood that the phrase “retaining orsupporting an applied load” encompasses one or more of the following:(1) retaining an applied load; (2) supporting an applied load; (3)retaining and supporting the same or different applied load; and (4)retaining or supporting the same or different applied load. The system100 comprises header stack 101 comprised of a plurality of header units110. Header units 110 are preferably formed from pre-cast concrete, butother suitable materials could be used. It should be understood that thepresent invention is not limited to the use of pre-cast concrete forheader units 110. There is an active reinforcement element 115configured to cooperate with the header stack 101 so thatpost-tensioning the active reinforcement element 115 imparts acorresponding pre-stressing force into the header stack 101. Thepre-stressing force applied to the active reinforcement element 115 istransferred to the header stack 101 at predetermined lock-off points111. Typically, one end of the active reinforcement element 115 ispreferably cast in the foundation 500 (best seen in FIG. 5) beneath theheader stack 101. The other end of the active reinforcement element 115,or at least some point distant from the end cast in the foundation 500,is stressed to induce the pre-stressing force. The distant end of theactive reinforcement element 115, or at least some point distant fromthe end cast in the foundation 500, must be locked off to maintain thetransfer of force from the active reinforcement element 115 to theheader stack 101.

A passive reinforcement element, disposed longitudinally through theheader stack 101, may be included within the duct(s) of the header stack101, which duct(s) is(are) formed by the passthrough ducts 116 of theheader units 110. Such passive reinforcement element would, typically,commence within the foundation element 500, and would be bonded to theheader stacks via a process of grouting. Such passive reinforcementelement, where included, would work with the active reinforcementelement 115 in order to assist the header stack 101 to meet a particularstructural performance requirement.

The system may also include passive reinforcement elements 705 (see, forexample, FIGS. 7 a and 7 b) that extend through passthrough ducts 125 inat least one of the header units 110. Passive reinforcement elements mayeither extend vertically or transversely with respect to header unit110. The passive reinforcement element 705 may be configured such thatit does not carry load distributed in the header stack 101. However,vertical or longitudinal passive reinforcement elements may beconfigured to account for additional compressive capacity at thecritical sections of the header stack 101 and/or to improve performanceof the critical sections under overload conditions.

The passive reinforcement elements 705 may also be useful to provideshear-dowel action between pre-cast components and cast-in-placeconcrete components, or other secondary structural members, in order towithstand shear-type loads that develop at the interface between suchcomponents (e.g., soil loads that would first be resisted bycast-in-place secondary structural members 130 c). The passivereinforcement element 705 preferably extends transversely through apassthrough duct 125 in the header unit.

The passive reinforcement element 705 may also be configured to transfertransverse forces between the header stack 101 and the secondarystructural elements adjacent one or both sides of the header stack 101.In such circumstance, the passive reinforcement element 705 may bebonded and/or mechanically connected to the header unit 110, with suchconnection being established over a predetermined portion of thereinforcement element 705. That is, suitable bond break is establishedover sufficient distance of the outer portion or portions of suchpassive reinforcement element 705 which portion or portions of thiselement 705 are adjacent the “outer” zones of the header unit 110 sointersected in order to prevent deleterious effects to the concrete ofthe header unit 110 within these “outer” zones common to both of theintersecting elements 110 and 705.

The passive reinforcement elements 705 may be placed within pre-castheader unit 110 during casting, as may be the case if the transverse(perpendicular to direction of active reinforcement elements andperpendicular to the front-to-back axis of the header unit) passivereinforcement element was expected to carry compressive forces intoand/or through the header unit 110. Alternatively, the passivereinforcement elements 705 may be fed through the transverse ducts 125after the associated header unit(s) 110 have been placed in their finalpositions. The ducts 125 that would be included in the header unit 110in the latter case allow for several behavioral characteristics. First,from the standpoint of structural performance enhancement of thestructural member, or panel, 130 b (see FIG. 12), between the headerstacks 101, where transverse ducts 125 are located in the header units110 to align with the rear reinforcement of the panel 130 b, the passivereinforcement elements 705 enable the development of moments at the endsof the panels 130 b. Second, where these passive reinforcement elements705 are required to sustain tension forces, the presence of the ducts125 prevents the tensile strains generated within the passivereinforcement elements 705 from attempting to transfer load, viabonding, to the header unit 110 through which it is passing. Third, thestructural interdependence, via force continuity through the headerstacks 101, that the presence of the transverse passive reinforcementelements 705 provide, ensures a greater lateral stability of the system.

The concrete components that comprise the header stacks 101 may beeither relatively large in size or quite small, and possess relativelyhigh load resistance capacity. The system designer is provided withconsiderable design flexibility in that header stacks 101 may be chosenfrom one or more of the range of header units available and which headerstacks so formed may be spaced at different spacings to suit differentload resisting requirements on the retaining wall via the use ofdifferent structural member lengths. Also design flexibility isavailable via the use of different arrangements of the components withinthis group. Various arrangements are shown in FIGS. 8-10, and will bedescribed in more detail below. Design flexibility is further enhancedvia the use of complementary structural elements 1100 such as thetieback transfer beams, as discussed below.

The desired or preferred pre-stressing force magnitude(s), pre-stressingforce location(s) and variation(s) associated with each header stack, asrequired by the designer, may be accommodated by using different typesof pre-stressing tendon, different total areas of pre-stressing tendon,as the active reinforcement elements 115, and by varying the amount ofpre-stressing force imparted into these active reinforcement elements115 together with varying the location(s) of the resultant force(s).

In one embodiment of the invention, the header units 110 that make upthe header stack 101 are shaped in a substantially “dog-bone”configuration as shown, for example, in FIGS. 3 and 6 a-6 e. Such headerunits 110 comprise a center element 118 having a top face 118 a, and abottom face 118 b; a first end element 112 disposed at one end of thecenter element 118; and a second end element 114 disposed at another endof the center element 118. The first end element 112 and second endelement 114 are preferably integrally formed with the center element118. The first end element 112 and the second end element 114 each havea top face 112 a, 114 a and bottom face 112 b, 114 b respectively thatare coplanar with the top face 118 a and bottom face 118 b of the centerelement 118. Exemplary embodiments of these headers 110 are best seen inFIGS. 6 a-6 e, and 7 a-7 c, and 21 a-21 d.

The header units 110 can be either symmetrical or asymmetrical about thecenter element 118. In other words, the header units 110 may besymmetrical or asymmetrical about a line perpendicular to an axis of theheader unit 110. FIGS. 6 a and 6 d illustrate two embodiments of asymmetrical header unit 110 that is symmetrical about one dashed lineperpendicular to the longitudinal axis of the header units of FIGS. 6a-6 e. FIGS. 6 b and 6 c show two embodiments of an asymmetrical headerunit 110 that are asymmetrical about the dashed line.

It is possible for the header units 100 to be asymmetrical about a planeextending along the length of the header unit 100. For example, theheader unit 100 could have one flat side. Such a header unit 100 couldbe used at the end of a retaining wall as a “finishing” header unit.Additionally, two such header units could be positioned with their flatsides abutting where a complete break in the wall is desired.

The header units 110 can be further classified as either main headerunits 110 m or sub-header units 110 s. The main header units 110 m aredouble-headed (i.e., have both a first end element 112 and a second endelement 114), or single-headed (i.e., have only a first end element112). The sub-header units 110 s also are either double-headed orsingle-headed. In any given header stack 101, either one of the mainheader units 110 m or sub-header units 110 s may be symmetrical orasymmetrical. The principal distinction between the main header units110 m and the sub-header units 110 s is that the main header units 110 mtypically extend past the sub-header units 110 s in a header stack 101.However, it is also possible for the sub-header units 110 s to beidentical to the main header units 110 m. For example, FIG. 1 depicts aheader stack 101 having two sections, an upper section 101 a and a lowersection 101 b. The upper most sub-header unit 110 s in the lower section101 b is geometrically identical to the lower most main header unit 110m in the upper section 101 a. The system 110 can be comprised entirelyof main header units 101 m or may be both main header units 110 m andsub-header units 110 s.

It is preferred that the faces of at least one of the first 112 andsecond 114 end elements have a curved portion 2101. Such a curvature(best seen in FIGS. 21 a-23) allows for an optimized bearing line of thestructural member 130 onto one of the header units 110. In that manner,any slight rotational deviation of the header stack 101 about itslongitudinal axis, from the most desired position, will not compromisethe integrity of the header units 110. Furthermore, the structuralmember 130, or stretcher will not be subjected to loading distributionssignificantly different from those intended in the designconsiderations.

In order to maintain an interlocking relationship between the headerunits 110, there are shear keys provided on the header units 110. Theshear keys comprise a plurality of indentations 120 on one of the top118 a and bottom 118 b faces of the center element 118 and a pluralityof protrusions 122 on the other of the top 118 a and bottom 118 b facesof the center element 118 corresponding to the plurality of indentations120. The protrusions 122 on each sub-header unit 110 s and main headerunit 110 m are configured to engage the corresponding indentations 120in an adjacent header unit 110. The indentations 120 and protrusions 122may also be provided on the first end element 112 and/or second endelement 114. The indentations 120 and protrusions 122 may also beprovided on part of the first end element 112 and/or part of the secondend element 114. Where such indentations 120 and protrusions 122 areprovided on the first end element 112 and/or second end element 114, oron parts thereof, these indentations 120 and protrusions 122 arepreferably continuous and geometrically consistent with such associatedfeatures that are provided on the center element 118. Preferably, asshown, for example, in FIGS. 7 a-7 c and 21 a-21 d, the shear keyscomprise first corrugations 120 a on one of the top 118 a and bottom 118b faces of the center element 118, and second corrugations 122 a on theother of the top 118 a and bottom 118 b faces of the center element 118corresponding to the first corrugations 120 a. The second corrugations122 a on each sub-header unit 110 s and main header unit 110 m areconfigured to nest with the corresponding first corrugations 120 a in anadjacent header unit 110. The first and second corrugations 120 a, 122 amay also be provided on the first end element 112, or part thereof,and/or second end element 114, or part thereof. Where such first andsecond corrugations 120 a, 122 a are provided on the first end element112, or portion thereof, and/or second end element 114, or portionthereof, these corrugations 120 a, 122 a are preferably continuous andgeometrically consistent with such associated features that are providedon the center element 118.

There are a plurality of passthrough ducts 116 provided in the headerunits 110 that are configured to receive the active reinforcementelements 115 and/or passive reinforcement elements 115 p, where suchpassive reinforcement elements 115 p are present in the header stack andhave longitudinal orientation with the header stack 101. The passthroughducts 116 can be any size or shape, but are preferably cylindrical inconfiguration, having axes parallel to the longitudinal axis of theheader unit 110. The first end element 112 defines a first passthroughduct 116 a and the second end element 114 defines a second passthroughduct 116 b. The center element 118 may or may not be provided with oneor more passthrough ducts 116 to receive active reinforcement elements115 or passive reinforcement elements 115 p. There are also a pluralityof passthrough ducts 125 that extend transversely through the headerunits 110 to receive passive reinforcement elements 705. Each of thepassthrough ducts 125 are preferably lined with a conduit that preventsthe passive reinforcement element 705 from bonding with each individualheader unit 110, and allows for the ready installation of the element705 through the header unit 110 after the header unit 110 has beenplaced into its final position within the header stack 101. Otherstructural associations between the transverse passive reinforcementelement 705 and the header unit 110 are discussed above.

The header units 110 can be constructed to suit any particular need.They can be designed to accommodate changes in the features such asgeometry detail, size, number and location of passthrough ducts 116,125; type, size, shape, and location of the shear keys on the top andbottom surfaces; etc.

In one embodiment of the present invention, the active reinforcementelements 115 are internally threaded in the header units 110 through thepassthrough ducts 116. The active reinforcement elements 115 are able tobe locked off at lock-off points 111 in lock-off recessions 138 in theheader units 110. Various lock-off elements 140 are provided to securethe active reinforcement element 115 after a pre-stressing force hasbeen applied. The lock-off point is the point at which thepost-tensioning force is imparted to the header stack 101. There areinternal lock-off elements 140 to secure the active reinforcementelements 115 within the lock-off recessions. While the lock-off elements140 are depicted in FIGS. 1 and 2 as being planar with the top surfaceof the header units 110 (i.e., within a lock-off recession 138 in thetop surface of the header unit 110), it would also be possible toprovide a lock-off recession in the bottom of the header unit 110 andthe lock-off element(s) 140 would then extend into the header unit 110above. For any lock-off point that is located within the header stackand between such complementary structural elements such as thefoundation element, a tieback transfer beam 1100, or capping beam, thereis another geometric arrangement wherein the lock-off recess necessaryfor the lock-off point, in order to accommodate lock-off elements 140,may be accommodated by a lock-off recession in the top surface of theheader unit 110 associated with and “below” the lock-off point and acomplementary and associated lock-off recession in the bottom surface ofthe header unit 110 associated with and “above” this same lock-offpoint.

In an alternative embodiment of the invention, the active reinforcementelements 115 may be disposed external to the header stack 101. In such aconfiguration, there are lock-off elements 1610 (best seen in FIGS.16-18) configured to secure the active reinforcement element 115. Asseen in FIGS. 19 and 20, the active reinforcement elements 115 may bedirected through a harping element 1910 at a harping point 1905. Theharping element 1910 is configured to redirect the active reinforcementelement 115 such that the active reinforcement element 115 forms aseries of substantially straight segments 1901, 1902, 1903. The activereinforcement element 115, when directed through a harping element 1910is still preferably locked off using a lock-off element 1610 (best seenin FIGS. 16 and 17). The active reinforcement element 115, when directedthrough a harping element 1910 may additionally and/or alternatively belocked off at such structural elements as a tieback transfer beam 1100,capping beam, or other complementary structural element. In theconfiguration depicted in FIG. 19, the lock-off element 1610 would bepositioned at a point distant from the harping element located atharping point 1905, or the active reinforcement element 115 may belocked off at such other structural element as a capping beam or tiebacktransfer beam element where such are part of the structuralconfiguration. The harping element is preferably not a lock-off element.The harping element 1910 simply serves to redirect the compressiveforces induced by active reinforcement element 115 and is not configuredas a lock-off point. The harping element 1910 simply redirects thedirection of the force being imparted by the active reinforcementelement 115 to the header stack 101.

The header stacks 101 may include a plurality of active reinforcementelements 115. The active reinforcement elements 115 may be both internal(i.e., directed through the passthrough ducts 116 in the header units,and, thus, the ducts that are formed via the successive abutting ofthese passthrough ducts 116 of such header units) and external (i.e.,directed through lock-off elements 1610 and harping elements 1910external to the header stacks 101). Such external active reinforcementelements 115 may also be situated between the header stacks 101 andconfigured to cooperate with the header stacks 101 via their interactionwith such structural elements as a foundation element, tieback transferbeam, capping beam, or other complementary structural element. Also, inconjunction with such external active reinforcement elements 115transfer and/or lock-off points may be located on and/or in suchcomplementary structural elements. The header stacks 101 mayalternatively have only internal active reinforcement elements 115 oronly external active reinforcement elements 115. Further, thesestructural systems may, in conjunction with such internal and/orexternal active reinforcement elements 115, also include passivereinforcement elements 115 p, which elements 115 p would pass throughpassthrough ducts 116 and be bonded to the duct formed in the headerstack 101.

Most header stacks 101 possess a plane of symmetry, which is thevertical plane containing the longitudinal axis of the header stack 101.Where such plane of symmetry of the header stack 101 exists, it ispreferable that the pre-stressing tendons such as active reinforcement115 be placed in a symmetrical fashion about this plane of symmetry andthat the active reinforcement elements 115 be stressed such that theresultant force lies essentially within this same plane of symmetry.Such stressing regime is peculiar to each header stack 101, and may bethe same as, or different from, that stressing regime that is associatedwith the header stack adjacent.

Coupled between each header stack 101 are structural members 130 thatmay resist soil loading directly. The loads sustained by such secondarystructural members 130 are transferred to the header stacks 101. Theheader stacks 101 transfer the accumulated loads to the foundations 500,and to any other elements that are designed to restrain these headerstacks 101 such as complementary structural elements 1100 (explained inmore detail below). The structural members 130 may take many forms. Thepreferred structural member 130 for use with the present embodiment is astretcher 130 a and is depicted in FIGS. 1-5, 8-11, and 22-26 b.Stretcher 130 a is preferably made from pre-cast concrete. There is asecondary passthrough duct 136 in the structural member 130 that isconfigured to receive the active reinforcement element 115. There may bea plurality of secondary passthrough ducts 136 in the stretchers 130 a,but at least one of the secondary passthrough ducts in the stretcher 130a must be in registry with at least one of the passthrough ducts 116 inthe main header units 110 m. The secondary passthrough duct 136 in thestructural member 130 may be configured to receive a passivereinforcement element 115 p.

The structural member 130, such as a stretcher 130 a, can be coupledbetween two main header units 110 m such that it abuts the sub-headerunit 110 s between the two main header units 110 m. The stretcher 130 acan be positioned between one of the first end element 112 and secondend element 114 of the main header units 110 w. Alternatively,stretchers 130 a can be positioned between each of the first endelements 112 and second end elements 114 of the main header units 110 w.In other words, there can be structural members 130, or stretchers 130a, on both sides of the header stack 101 or on only one side of theheader stack 101. However, the stretcher 130 a arrangement need not beidentical on both sides of the header stacks 101. For example, in FIG.10, there are stretchers 130 a coupled to only a portion of one side1000 of the header stacks 101 and there are stretchers 130 a coupled tothe entire span of the header stacks 101 on the opposite side 1005. Notethat in FIG. 4 the stretchers 130 a in the “rear” of the system (whichstretchers have been omitted from the drawing), where the soil massbeing retained (not shown) would be positioned with respect to the wall,are not directly contributing to the resistance of the principal loadsas are being resisted by the header stack 101, when those principalloads are applied. In such a configuration, the zone of the stretchers130 a that intersects with the main header units 110 m may contribute tothe resistance of the compression force that is transferred to theheader stack 101 by the pre-stressing of the active reinforcementelements 115 where such pre-stressing occurs prior to the application ofthe principal external loads.

The structural member 130 may also consist of Cast-In-Place (CIP)concrete panels 130 c (see FIGS. 12 and 13). The CIP concrete panels 130c have two distinct roles. The first role remains the direct retentionof the soils and the transfer of these soil loads to the header stacks101. The second role is to provide additional compression area in theresistance of the primary bending moments that develop over the heightof the wall. Alternatively, with different loading and structuralconfigurations, these CIP panels may accommodate active and/or passivereinforcement elements, 115 and/or 115 p, where such elements areconfigured to work with and to assist the header stacks in resisting theaccumulated loads assumed by same.

Note that the effectiveness of this composite action is highly dependenton the position of the CIP concrete panels 130 c relative to the headerstack 101 cross-section. Also, the effectiveness is equally dependent onthe nature and location of the equilibrating reaction forces thatrestrain the wall structure.

The use of cast-in-place concrete panels 130 c for the secondarystructural members 130 provides great flexibility for a design engineer.In particular, it is a very simple matter to vary the spacing betweenheader stacks 101. Moreover, the direction of a retaining wall(described in more detail below with respect to FIGS. 8-13) may bechanged with ease, and as many times as the site and functionalconditions demand. The retaining walls or other type of modularconstruction constructed from header units 110 coupled with CIP panels130 c may include plan curvatures, and reverse curvatures. Via the useof Task Specific Construction equipment (TSC equipment), the panels maybe constructed using slip-forming techniques. This translates into veryrapid construction of high retaining walls.

As with all the other embodiments presented herein, use of CIP panels130 c allows for the ready inclusion of one or more complementarystructural elements 1100, such as a tieback transfer beam (see, forexample, FIG. 11). These complementary structural elements 1100 providemuch additional versatility for systems 100. They may be included atdifferent locations up the height of the wall and, because of thereaction forces that are provided from the ground anchors 1115, allowfor economic retaining wall construction to great height.

The construction of complementary structural elements 1100, and theseating of the first header unit 110 on top of the complementarystructural element 1100, is facilitated via the use of Task SpecificConstruction equipment 1480 (TSC equipment), such as that depicted inFIGS. 15 a and 15 b. This will be described in more detail below withrespect to a retaining wall fabricated in accordance with the presentinvention.

Referring to FIGS. 11 and 13, a system with a complementary structuralelement 1100 is shown. Where loading to be resisted by the retainingwall structure is large and where adequate ground anchor 1115 capacitymay be developed within legally available ground space or right-of-ways,the use of these complementary structural elements 1100 providessolution opportunities that will tame very demanding retention and/orstabilizing problems. In general, the complementary structural element1100 reduces the loads that are “seen” by the foundation element(s). Aspreviously described, the load-path that exists in a retaining wallstructure is as follows.

The soils being retained exert pressure on the retaining wall'sstructural members 130. These elements may be stretchers 130 a, or theymay be pre-cast panels 130 b, cast-in-place (CIP) concrete panels 130 c,or some other type of structural component. Such structural members 130transfer these loads to the header stacks 101. The header stacks 101resist the accumulated soil loads, and other loads where such are beingresisted by the wall system, and transfer these loads to the structuralmembers that provide the equilibrating reaction forces. Such reactionelements and/or members may be the foundation elements 500, 1450,tieback transfer beams 1100, capping beams, and/or other complementarystructural elements, which themselves may be further assisted by otherstructural elements, such as associated ground anchors 1115, thatcollaborate in the development of the required reaction forces. Therewill be soil pressures exerted directly on the header stacks 101.However, these pressures depend on the exposed surfaces of the headerunit 110 and its geometric characteristics as well as the spacingbetween the header stacks 101 and the characteristics of the soils beingretained.

The foundation 500, that the header stack 101 is constructed on, andcomplementary structural elements 1100 if present, provide the necessaryreaction forces for and directly to the header stack 101 of theretaining wall. In certain structural configurations, for example inpure cantilever arrangements, these reaction forces may be provideddirectly, and wholly, by the foundation beam/footing element itself.Alternatively, in certain configurations of these systems, additionalequilibrating reaction forces may be provided via other elements such asground anchors 1115 and/or piles, for example, to the foundation beam(pile cap, if piles are being used in conjunction with the foundationelement 500, 1450). Other structural elements, such as ground anchors1115, may also provide equilibrating reaction forces to complementarystructural elements 1100 where present, and to the capping beams wherepresent and where such resisting forces are required at these levels.

As seen in FIGS. 11 and 13, the complementary structural element 1100 isa tieback transfer beam preferably disposed between two header units 110and extending between two or more of the header stacks 101. A groundanchor 1115 may be coupled to the complementary structural element 1100to provide additional resistance to an applied load. Other structuralelement(s) may also, or alternatively, be coupled to the complementarystructural element 1100 to provide additional resistance to an appliedload. The complementary structural element 1100 can extend across theentire length of a construction or can be located between only someheader stacks 101 that comprise the construction. The complementarystructural element 1100 is provided with passthrough ducts 1116 that areconfigured to receive an active reinforcement element 115 or passivereinforcement element 115 p. As with the passthrough ducts 136 in thestretchers 130 a, the passthrough ducts 1116 in the complementarystructural element 1100 must be in registry with the passthrough ducts116 in the header units 110.

The complementary structural elements 1100 are also provided with apassthrough channel 1130 extending through the complementary structuralelement 1100. A ground anchor 1115 is coupled to the complementarystructural element 1100 and is configured to extend through thepassthrough channel 1130. Depending upon the direction of force requiredfrom the ground anchor 1115, the passthrough channel 1130 can beprovided in a variety of positions. For example, as seen in FIG. 11,there is a raised portion 1120 extending from the complementarystructural element 1100 that is in communication with the passthroughchannel 1130 for receiving the ground anchor 1115. Although the figureillustrates the raised portion 1120 on the top of the complementarystructural element 1100, it would be desirable in certain situations tohave the raised portion 1120 on the bottom of the complementarystructural element 1100. Further, it would be desirable in certainsituations to have a raised portion 1120 on the top of the complementarystructural element 1100 as well as have (together with) a raised portion1120 on the bottom of the complementary structural element 1100 in closevertical proximity with the raised portion 1120 on the top of thecomplementary structural element 1100. In FIG. 13, the ground anchor1115 extends from a front face 1112 of the complementary structuralelement 1100 through the passthrough channel 1130.

Referring now to FIGS. 27 a-33, another embodiment of the components ofa system 100 is depicted. The header units 2700 that make up the headerstack 2701 in this embodiment comprise a top face 2790 and a bottom face2780; a base element 2710 having a first end 2702 and a second end 2704;a head element 2712 having a first end 2706 and a second end 2708; and apair of side elements 2714 extending between the first end 2702 and thesecond end 2704 of the base element 2710 and the first end 2706 andsecond end 2708 of the head element 2712. Either the base element 2710or head element 2712 preferably extends past the side elements 2714 suchthat a flange 2705 is formed adjacent one or both side elements. Theside elements 2714 may also couple with the base element 2710 such thatan indentation 2707 is formed adjacent the base element 2710 (see FIG.27 a). Alternatively, the side elements 2714 may couple with the headelement 2712 to form an indentation 2707 adjacent the head element 2712(see FIG. 27 h). The flange 2705 or indentation 2707 is configured tocouple with a structural member 130. The header units 2700 of thisembodiment have an open cell 2709 defined by the base element 2710, headelement 2712 and side elements 2714. Such a configuration significantlydecreases the weight of the header unit 2700 without sacrificingstrength and performance of the system. Such configuration significantlyallows for the optimization of strength, stiffness, and relatedproperties of the components, and structure constructed with suchcomponents, versus the use of materials to obtain such structuralperformance.

The arrangement depicted in FIGS. 27 a and 27 b is characterized by theconvergence of the header webs or side elements 2714 from the back orbase element 2710 of each unit 2700 to the front or head element 2712.The angle of convergence of these units may vary.

A retaining and/or support structure formed with these header units 2700may employ (1) pre-cast concrete panels 130 b, (2) cast-in-placeconcrete panels 130 c, (3) a secondary structural element formed fromthe use of shotcrete 130 d (see, for example, FIG. 28 and FIG. 29), or(4) some other suitable material and/or suitable structuralconfiguration for such secondary structural elements 130.

The header stacks 2701 formed with these header units 2700 are tied, viathe main soil retaining elements (the secondary structural member 130),where desired. The effectiveness of the tie will depend on theparticular details of the design. Obviously, the retaining walls and/orsupport structures so formed are also tied horizontally by thefoundation elements 500, 1450, the complementary structural elements(where included) 1100, and the capping beam(s) 3409 (where included).

It is important to note that, while these header units 2700 may bedesigned and configured to perform their structural roles compositelywith, for example, cast-in-place concrete panels 130 c, there areseveral other ways that these versatile systems may be employed.Consider, for example, the use of reinforced or unreinforced shotcretearches 130 d between the header stacks 2701 as shown in FIGS. 28 and 29.Or, consider the use of pre-cast concrete panels 130 b, which panels mayalso be pre-stressed by a pre-tensioning procedure, which are connectedto the header stacks 2701 via reinforced cast-in-place concrete“welding” or “joining” columns or elements. These connecting columns orelements, with their incorporated continuity reinforcement elements andconnections, would cause all the elements brought together in thisarrangement to act as an integrated structural system.

The header units 2700 may also have a single set of continuityreinforcing bars 2775 per base element 2710 and/or head element 2712(see FIGS. 27 c-270 located to match the forward rebar of thecast-in-place panels 130 c where such cast-in-place panes areincorporated between or abutting adjacent header stacks 2701. This“forward” rebar has two roles. One is to provide for positive connectionof the header stacks 2701 to the CIP panels 130 b or 130 c between them,abutting them, and on either side of them. This continuity of steelwould be provided via mechanical connectors. The second role is toprovide a rapid and accurate means by which the forward reinforcing matof the CIP panel 130 c may be fabricated and/or installed.

As with the header units 110 in the embodiment described previously, theheader units 2700 depicted in FIGS. 27 a and 27 b can be produced with avariety of continuity and/or connection rebar configurations. This is,in general, true of all the header units of the present invention thatare designed to work integrally with cast-in-place concrete 130 c and/orwhere positive continuity and/or connection need to be provided forpre-cast panels 130 b placed between header stacks 2701. One of the mostcommon reasons for a “second” set of these bars is to provide for theimmediate development of negative moment at the ends of these CIP panels130 c, where they butt the header stacks 2701 (as is indicated in FIG.32). These continuity rebar sets, which provide for the development ofthese negative moments at the ends of the panels 130 c, and/or 130 b,may be the only sets provided in a header unit 2700. These continuityreinforcement elements preferably pass through the header units 2700within transverse ducts 3210 (see FIG. 32), which transverse ducts aretypically included within the header units 2700 during theirmanufacture.

As with the header units 110 in the embodiment described previously, thepassive reinforcement element may also be configured to transfertransverse forces between the header stack 2701 and the secondarystructural elements 130 c and/or 130 b abutting or adjacent one or bothsides of the header stack 2701. In such circumstance, the passivereinforcement element 2777 may be bonded and/or mechanically connectedto the header unit 2700, with such connection being established over apredetermined portion of the passive reinforcement element 2777, only,where such passive reinforcement element 2777 is continuous through theheader unit 2700. As with the header units 110, where the reinforcementelement 2777 is not a continuous element through the header unit 2700,such element 2777 may terminate within the header unit and protrude outone side of the header unit 2700. That is, suitable bond break isestablished over sufficient distance of the outer portion or portions ofsuch passive reinforcement element 2777 which portion or portions ofthis element 2777 are adjacent the “outer” zones of the header unit 2700so intersected in order to prevent deleterious effects to the concreteof the header unit 2700 within these “outer” zones common to both of theintersecting elements 2700 and 2777.

Header units 2700 may be relatively large or small in size and possesshigh load resistance capacities. Typically, their installation would befound in situations where very large retention capacity is demanded ofthe retaining structure. This large retaining capacity may be furtherextended and/or enhanced with the use of complementary structuralelements 1100, which complementary structural elements themselves may,or may not, be augmented with such elements as ground anchors, which tiein, and/or frame in, to the structural system.

As a general note, the degree to which greater efficiencies are derivedfrom the composite systems, where one of the composite systems are used,will depend on several factors. One factor is where the cast-in-placeconcrete panel 130 c (or pre-cast concrete panels 130 b where suchpanels are being made to act compositely with the header stacks 2701associated) frames into the header stack 2701. This in turn depends onthe geometry of the header unit 2700 being used, that is, it depends onthe position, on the header unit 2700, where the CIP panel, or panels,130 c, or pre-cast panels 130 b, is/are coupled. The header unit 2700shown in FIGS. 27 a and 27 b places the panel 130 c and/or 130 b at therear of the header stack 2701 while the header units 2700 shown in FIGS.27 g and 27 h, for example, place the concrete panel 130 c, or 130 b,near the front of the header stacks 2701 so formed.

A second factor is the presence of complementary structural elements1100 such as a tieback transfer beam. The presence of one or more ofthese complementary structural elements 1100, up the height of a wall,not only reduces the loading on the foundation elements 500, 1450, butalso directly influences the moment distributions over the height of thewall structure and, in particular, the header stacks 2701 of the wallstructure. The moment profile and magnitudes will have a directinfluence on the choice of one header type and size over that ofanother.

The complementary structural elements 1100 acting in conjunction withother elements such as ground anchors 1115, are not the only way inwhich lateral restraint may be applied to the retaining wall(s) 3100 atone or more levels up the structure. Where, for example, a“cut-and-cover” is required, and the walls are to be constructed on oneor both sides of the cut, beams frequently reach from one side of the“cut” to the other. These spanning beams may then be utilized to act asstruts, and thereby provide horizontal restraint to the walls at levelsabove the foundations.

The header units 2700 depicted in FIGS. 27 g and 27 h are characterizedby the divergence of the header webs, or side elements 2714 from theback or base element 2710 of each unit 2700 to their front or headelement 2712. The header stacks 2701 formed with header units 2700 inFIGS. 27 g and 27 h are typically not directly tied together, except atthe foundation element(s) 500, 1450, the capping beam(s), and anycomplementary structural element or elements 1100, that may be included.The retaining and/or support structure formed with the header units 2700in FIGS. 27 g and 27 h may employ (1) pre-cast concrete panels 130 b,(2) cast-in-place concrete panels 130 c, (3) a secondary element formedfrom the use of shotcrete 130 d, or (4) some other suitable materialand/or suitable structural configuration for such secondary structuralelements 130.

The header unit 2700 depicted in FIG. 27 g with the single passthroughduct 2716 at the rear of the header unit 2700, is specifically designedto form header stacks 2701 that only behave as cantilevering structures.That is, they are constructed on the retaining wall's foundation, whereall the restraint is provided by the moments and shear forces thatdevelop at the interface between the header stacks and the foundation.

Note, however, where there exists the possibility of reverse momentsoccurring, as might be the case if the retaining wall and any attachedappurtenances were to be subjected to earthquake loading, then a nominaland sufficient capacity to withstand such infrequent events would berequired. In such a case, the use of the header unit depicted in FIG. 27h with an additional forward passthrough duct 2716 would be in order.Assuming the wall is a cantilevering structure without assistance from acomplementary structural element 1100, for example, the header unitwould be used without necessarily employing active reinforcementelements 115 through the forward duct 2716. This would be the casebecause the CIP concrete panels 130 c on either side of the headerstacks 2701 would be designed with sufficient vertical reinforcing steelto provide, in composite action with the header stacks 2701, thenecessary reversed moment capacity.

The header units 2700 in 27 a, 27 b, 27 d, 27 f, and 28 through 33 arewell suited to resisting very large loads. In particular, where theretaining wall 3100 (see, for example, FIG. 31) is cantilevering fromthe foundation element(s), because of the large moments that can beresisted with this system, the structure may competently retain verylarge soil loads. Additionally, the system can readily includestructural elements that cantilever out from the face of the wall, orfrom the top of the wall as shown, for example, in FIGS. 34 a, 34 b and34 f, or may support other structural elements using other supportingmechanisms.

As seen in FIGS. 34 a, 34 b and 34 f, the modular construction 800 maybe configured to support a cantilever structure 3450 such as a roadway,sidewalk, etc. The modular construction 800 comprises a header stack2701, 101 comprised of header units 2700, 110. One or more complementarystructural elements 1100 may also be incorporated where desired.

The header units 2700 depicted in FIGS. 27 e and 27 f are characterizedby their webs, or side elements 2714, being parallel. Note that theheader units 2700 shown in FIG. 27 e do not have a cell 2709, while theheaders in FIGS. 27 a, 27 b, 27 c, 27 d, 27 f, 27 g, 27 h and 28 do havea cell 2709. This is because the header unit depicted in FIG. 27 e isthe smallest in the range of such header units 2700 which header unitspossess parallel webs or side elements 2714.

The system having the various types of header units 2700 depicted inFIGS. 27 a-h may use passive reinforcement elements 2775 and 2777, orother transverse passive reinforcement elements, that extend throughpassthrough ducts 3210 (as seen for example, in FIG. 32) in at least oneof the header units 2700. The passive reinforcement element 2775, 2777are configured such that it does not carry load distributed in theheader stack 2701. The passive reinforcement elements 2775, 2777 mayalso be useful to provide shear-dowel action between pre-cast componentsand cast-in-place components to withstand loads (e.g., soil loads thatwould first be resisted by secondary structural members 130). Thepassive reinforcement element 2775, 2777 preferably extends transverselythrough a passthrough duct 3210 in the header unit 2700.

Other, longitudinally aligned passive reinforcement elements, whichelements are disposed within passthrough ducts 2716, and which passivereinforcement elements are subsequently bonded to the ducts so formed inthe header stacks 2701, may be configured to account for additionalcompressive capacity at the critical sections of the header stack 2701and/or to improve performance of the critical sections under overloadconditions.

The passive reinforcement elements 2775, 2777 may be placed within theheader units 2700 depicted in FIGS. 27 c, 27 d, 27 e, 27 f, and FIG. 32during casting, as would be the case if the transverse passivereinforcement element, for example element 2775, was expected to carrycompressive forces, or after the header unit 2700 was in place. Theducts 3210 that would be included in the header unit 2700 in the lattercase allow for several behavioral characteristics. First, from thestandpoint of structural performance enhancement of the panel 130 cand/or 130 b between and/or abutting the header stacks 2701, wheretransverse ducts 3210 are located in the header units 2700 to align withthe rear reinforcement of the panel 130 c and/or 130 b, the passivereinforcement elements 2775, or 2777 enable the development of negativemoments at the ends of the panels 130 c and/or 130 b. Second, wherethese passive reinforcement elements 2775, 2777 are required to sustaintension forces, the presence of the ducts 3210 prevents the tensilestrains generated within the passive reinforcement elements 2775, 2777from attempting to transfer load, via bonding, to the header unit 2700through which it is passing. Third, the structural interdependence, viaforce continuity through the header stacks 2701 that the presence of thetransverse passive reinforcement elements 2775, 2777 provide ensures agreater lateral stability of the system.

In order to maintain an interlocking relationship between the headerunits 2700, shear keys may be provided on the header units depicted inFIGS. 27 a-27 i, and as shown, for example, in FIGS. 27-33. The shearkeys comprise a plurality of indentations 2120 on one of the top 2790and bottom 2780 faces of each header unit 2700 and a plurality ofprotrusions 2122 on the other of the top 2790 and bottom 2780 faces ofthe header unit 2700 corresponding to the plurality of indentations2120. The protrusions 2122 on each header unit 2700 are configured toengage the corresponding indentations 2120 in an adjacent header unit2700. The indentations 2120 and protrusions 2122 are preferably providedon the head element 2712, base element 2710 and side elements 2714.Preferably, the shear keys comprise first corrugations 2120 a on one ofthe top 2790 and bottom 2780 faces of the header unit 2700, and secondcorrugations 2122 a on the other of the top 2790 and bottom 2780 facesof the header unit 2700 corresponding to the first corrugations 2120 a.The second corrugations 2122 a on each header unit 2700 are configuredto nest with the corresponding first corrugations 2120 a in an adjacentheader unit 2700. The first 2120 a and second 2122 a corrugations arepreferably provided on the head element 2712, base element 2710, andside elements 2714. However, it is possible to have corrugations on onlyone of the elements provided there were corresponding corrugations onthe same element of an adjacent header unit 2700. Where the shear keys,such as corrugations 2120 a, 2122 a, are provided they are preferablycontinuous and preferably geometrically consistent over those portionsof the head element 2712, base element 2710, and side elements 2714where such features are provided.

There may be a plurality of passthrough ducts 2716 provided in theheaders 2700 that are configured to receive active reinforcementelements 115 and/or passive reinforcement elements 115 p. Thepassthrough ducts 2716 can be any size or shape, but are preferablycylindrical in configuration. The head element 2712 and base element2710 can each define a passthrough duct 2716. The side elements 2714 mayor may not be provided with one or more passthrough ducts 2716 toreceive active reinforcement elements 115 and/or passive reinforcementelements 115 p. There are also a plurality of passthrough ducts 3210that extend transversely through the header units 2700 to receivepassive reinforcement elements 2775, 2777 as mentioned above. Where thetransverse reinforcement elements 2775, 2777 are continuous through theheader units 2700 and where such elements 2775, 2777 are not providedwith a capability to transfer transverse forces to the header units2700, pas through ducts 3210 are preferably lined with a conduit thatprevents the reinforcement element 2775, 2777 from bonding with eachindividual header unit 2700. As discussed previously, such elements2775, 2777 may be connected via bonding and/or mechanical connection tothe header units 2700, but, preferably, this connecting between theseelements 2775, 2777 and 2700 is over specifically limited lengths of theincorporated passive reinforcement elements, which elements 2775, 2777are prevented from bonding over their outer portion or portions of theirintersection with the concrete of the header unit 2700.

The header units 2700 can be constructed to suit any particular need.They can be designed to accommodate changes in the features such assize, number and location of passthrough ducts 2716, 3210; size, shape,and location of the shear keys on the top and bottom surfaces, etc.

In one embodiment of the present invention, the active reinforcementelements 115 and/or passive reinforcement elements 115 p are internallythreaded in the headers 2700 depicted in FIGS. 27 a-h through thepassthrough ducts 2716. The active reinforcement elements 115 are ableto be locked off at lock-off points 2810 in lock-off recessions 2812 inthe header units 2700, where these lock-off points require such lock-offrecessions. There are internal lock-off elements (not shown) to securethe active reinforcement elements 115 within the lock-off recessions2812, where these lock-off recessions are/may be required. Such activereinforcement element 115 may also be locked off at, on, or in, suchcomplementary structural elements 1100 as a tieback transfer beam and/orcapping beam.

In an alternative embodiment of the invention, the active reinforcementelements 115 may be disposed external to the header unit 2700 eitherwithin the cell of, or external to, the header unit 2700.

The header stacks 2701 may include a plurality of active reinforcementelements 115. The active reinforcement elements 115 may be both internal(i.e., directed through the passthrough ducts in the header units) andexternal (i.e., directed through lock-off elements external to theheader units). The header stacks 2701 may alternatively have onlyinternal active reinforcement elements 115 or only external activereinforcement elements 115. Such external active reinforcement elements115 may transfer their pre-stressing force or forces to the structuralassembly via force transfer points that are included in, on, or at suchstructural components as foundation elements 500, 1450, tieback transferbeams 1100, capping beams, or other complementary structural elements.Also, the internal active reinforcement elements 115 may utilize similarforce transfer points, in addition to, or alternatively to, transferpoints that are included within the cross-section of the header stack2701 header units 2700.

Coupled between each header stack 2701 are structural members 130 thatmay resist soil loading directly. The soil loads sustained by thesecondary structural elements 130 are substantially transferred to theheader stacks 2701. The header stacks 2701 transfer the accumulatedloads to the foundations, and to any other elements such as thecomplementary structural elements 1100, that are designed to restrainheader stacks 2701. The structural members 130 may take many forms.

The preferred structural member for use with the header units 2700 ofthe present embodiment is a concrete panel 130 b and/or 130 c disposedbetween, adjacent, or abutting each header stack 2701. The structuralmembers 130 are coupled to the header units 2700 at the indentationadjacent the base element 2710 or head element 2712. There may bepassive reinforcement elements 2775, 2777 that are pre-positioned in theindentation 2707 to connect to, and/or maintain the position of, thereinforcement elements of the panels 130 b and/or 130 c associated withthe header stack 2701. The structural element 130 may be a pre-castconcrete panel 130 b, cast-in-place concrete panel 130 c, or may be ashotcrete structural element 130 d. There may also be a bearing strip3030 (as indicated in FIGS. 30 and 31) or bearing element provided inthe indentation 2707. This bearing element 3030 ensures correct seatingof the panel 130 b against the header stack 2701 without the developmentof detrimental stress concentrations in either the panels of headerstack 2701. The bearing strip 3030 is preferably a fully competent andpliable material such as, for example, rubber, polyethylene, neoprene,and butylene, as appropriate to the structural role required of same3030. Similarly, FIG. 32 includes a crush strip 3038 which is situatedprior to “pouring” the concrete for a cast-in-place concrete panelagainst header stack 2701. The crush strip 3038 allows the CIP panel todeform under load without having a detrimental effect on the concrete ofthe header units 2700. Moreover, the crush strip 3038 ensures that theload from the panel 130 c is imparted as far into the header stack 2701as possible (i.e. as far from the extreme edges of the header stack aspossible).

A complementary structural element 1100, such as a tieback transferbeam, may be incorporated within a structural system which is comprisedpartially or largely of header stacks 2701, wherein such structuralelement 1100 is preferably disposed between two header units 2700 andextends between two or more of the header stacks 2701. A ground anchor1115 may be coupled to the complementary structural element 1100, ortieback transfer beam, or capping beam, to provide additional resistanceto an applied load. The complementary structural element 1100 isprovided with passthrough ducts 1116 that are configured to receive anactive reinforcement element 115, or passive reinforcement element 115p. The passthrough ducts 1116 in the complementary strut element 1100must be in registry with the passthrough ducts 2716 in the header units2700 where internal active reinforcement elements 115 and/or passivereinforcement elements 115 p are provided in conjunction with headerstacks 2701. Also, where external active reinforcement elements 115 areprovided in conjunction with header stacks 2701 passthrough ducts 1116in the complementary structural element 1100 must be in registry withsuch external active reinforcement elements 115.

The complementary structural elements 1100 are also provided with apassthrough channel 1130 extending through the complementary structuralelement 1100. A ground anchor 1115, or other suitable structural elementcapable of developing the necessary tension forces required at thatlocation by the particular structural installation, is configured toextend through the passthrough channel 1130, and is coupled to thecomplementary structural element 1100. Depending upon the direction offorce required from the ground anchor 1115, the passthrough channel 1130can be provided in a variety of positions. There can be a raised portion1120 extending from the complementary structural element 1100 that is incommunication with the passthrough channel 1130 for receiving the groundanchor 1115. Although it is preferred to have the raised portion 1120 onthe top of the complementary structural element 1100, it would bedesirable in certain situations, such as when the ground anchor 1115, orother suitable structural element capable of developing the necessarytension forces required at that location by the particular structuralinstallation, would need to extend in an upwardly direction, to have theraised portion 1120 on the bottom of the complementary structuralelement 1100. Further, it would be desirable in certain situations tohave a raised portion 1120 on the top of the complementary structuralelement 1100 as well as having a raised portion 1120 on the bottom ofthe complementary structural element 1100 in close vertical proximitywith the raised portion 1120 on the top of the complementary structuralelement 1100. The ground anchor 1115 can also extend from a front face1112 of the complementary structural element 1100 through thepassthrough channel 1130.

Referring to FIGS. 28-33, various configurations of a modularconstruction are depicted using header units 2700. The partial view of amodular construction shown in FIGS. 28-29 depicts header units 2700using active reinforcement elements 115 both internally (i.e., withinthe passthrough ducts 2716) and external to the header unit 2700. Thereis a shotcrete panel 130 d disposed between adjacent header stacks 2701.FIGS. 30 and 31, depict the use of pre-cast panels 130 b in between theheader stacks 2701 and the use of both internal and external activereinforcement elements 115. FIGS. 32 and 33 depicts the use of CIPpanels 130 c between header stacks 2701.

Referring now to FIGS. 24 a-26 b, the systems in the above embodimentscan also be arranged with corner closure stacks 2401 for situations inwhich the retaining wall 800 must be constructed in other than astraight line. The corner closure stacks 2401 comprise a plurality ofcorner closure units 2400 and a second active reinforcement element 2115configured to cooperate with the corner closure stack 2401 so thatpost-tensioning the second active reinforcement element 2115 imparts acorresponding pre-stressing force into the corner closure stack 2401.Each corner closure unit 2400 comprises a body element 2412 having a topface 2412 a and a bottom face 2412 b and a junction element 2414 havinga top face 2414 a and a bottom face 2414 b. The junction element 2414 ispreferably disposed at one end of the body element 2412 and may beintegrally formed with the body element 2412. The body element 2412 isessentially identical for different embodiments of the corner closureunits 2400. The junction element 2414, however, will vary inconfiguration depending upon the use of the corner closure stack 2401.For example, the junction element 2414 can be utilized with either aninternal or included angle 2422 as shown in detail in FIGS. 24 b and 25b or an external, or excluded angle 2424 as shown in FIGS. 24 c and 25c. The included angle 2422 and excluded angle 2424 can also be seen inFIGS. 24 d, 25 d, and 26 a. The junction element 2414 extends from thebody element 2412 in an angular configuration in order for it to receivethe secondary structural members 130 from the header stacks 101, 2701 towhich it is adjacent or between. The junction elements 2414 may extendoutwardly at any angle, but are preferably configured to form angles of90 degrees as in FIG. 24 b, 270 degrees as in FIG. 24 c, 135 degrees asin FIG. 25 b, and 225 degrees as in FIG. 25 c. The angle that is chosenwill be dependent upon numerous design considerations including thespacing between the header stacks 101, 2701 and the corner closurestacks 2401 as well as the dimensions of the header units 110, 2700 andcorner closure units 2400. The corner closure units 2400 are configuredsimilar to the header units 110, 2700 in that they are similarlyprovided with shear keys (not shown) (e.g., protrusions and indentationsor first and second corrugations) and passthrough ducts 2416. The cornerclosure stack 2401 may similarly be provided with external harpingelements 1910 to receive external active reinforcement elements 115.Passthrough ducts 2416 may also be configured to receive longitudinalpassive reinforcement elements 115 p.

The corner closure stacks 2401 are coupled to the header stacks 101,2701 by the structural members 130. Preferably, the structural member130 is disposed between junction elements 2414 of adjacent cornerclosure units 2400. The corner closure units 2400 preferably compriserecessions 2402 in the junction element 2414 that are half the height ofa typical stretcher 130 a (see, for example, FIGS. 24 b, 24 c, 25 b and25 c). In this regard, the stretcher 130 a is enclosed within theadjacent junction elements 2414. The recession 2402 in the junctionelement 2414 could also be equal to the height of the secondarystructural elements 130.

In order to close any large gaps that may result in a construction as aresult of using the corner closure stacks 2401, an augmenting stack 2430can be provided such as shown in FIG. 24 a and FIG. 24 d. The augmentingstack 2430 is essentially provided to, as the name suggests, augment themodular construction. The augmenting stack 2430 can be comprised of ascaled down version of the header units 110 such that it is able to fitwithin the space constraints created by the corner closure stack 2401and the adjacent header stack 101.

FIGS. 24 a, 25 a, and 26 b depict the use of the various corner closurestacks 2401 and augmenting stacks 2430. Each modular construction canmake use of a variety of corner closure units 2400.

Referring now to FIGS. 8-10, an exemplary modular construction 800 ofthe present invention is depicted. The pre-stressed modular construction800 comprises a plurality of header stacks 101 with a plurality ofstructural members 130 coupled to at least one of the header stacks 101.The header stacks 101 are comprised of a plurality of stacked headerunits 110. There is also preferably at least one active reinforcementelement 115 for each of the header stacks 101 with each activereinforcement element 115 being configured to cooperate with its headerstack 101 so that post-tensioning the pre-stressing tendon 115 prior toapplication of the applied load imparts a corresponding pre-stressingforce into its header stack 101 at least one lock-off point 111. In apossible alternative embodiment, the active reinforcement elements 115are not post-tensioned, thereby providing a vertically disposed passivereinforcement element. The modular construction is formed on foundation500.

Referring to FIG. 12, an alternative modular construction is shown. Themodular construction of FIG. 12 uses cast-in-place concrete panels 130 cbetween header stacks 101.

In another aspect of the invention, a pre-stressed modular construction800 for retaining or supporting an applied load is provided. Withreference now to FIGS. 22 and 23, the pre-stressed modular construction800 comprises a plurality of header stacks 101 with a plurality ofstructural members 130 coupled to at least one of the header stacks 101.The header stacks 101 of the modular construction 800 are configured asdescribed in the above embodiments. Either type of header unit 2700, 110described previously may be utilized to form a modular construction 800according to the present invention.

The pre-stressed modular construction 800 preferably comprises at leasttwo header stacks 2701, 101, wherein each of the header stacks 2701, 101being comprised of a plurality of stacked header units 2700, 110. Thereis also preferably at least one active reinforcement element 115 foreach of the header stacks 2701, 101, with each active reinforcementelement 115 being configured to cooperate with its header stack 2701,101 so that post-tensioning the active reinforcement element 115 priorto application of the applied load imparts a corresponding pre-stressingforce into its header stack 2701, 101 at least one lock-off point 111.As noted above, a preferred active reinforcement element is apre-stressing tendon such as the tendons shown in, for example, FIGS.14, 23, and 28-32. There is also a structural member 130 coupled to theat least two header stacks 2701, 101. The pre-stressed modularconstruction 800 further preferably comprises a tieback transfer beam1100 disposed between two of the header units 2700, 110 and extendsbetween the at least two header stacks 2701, 101. There is also a groundanchor 1115 coupled to the tieback transfer beam 1100. The structuralmember 130 can be a concrete stretcher 130 a, a pre-cast concrete panel130 b, a cast-in-place concrete panel 130 c, or a shotcrete panel 130 d.

In another aspect of the invention, a method of fabricating apre-stressed modular construction 800 for retaining or supporting anapplied load is provided. A foundation element 1450, 500 is firstprovided for the construction. On a site-by-site basis, the foundationelement 1450, 500 may be augmented by other structural elements, such asground anchors, piles, or other supporting/restraining elements, thatassist the foundation element 1450, 500 in resisting the forces that aretransmitted to it by the retaining and support structural system of thepresent invention. Referring to FIGS. 14 a and 14 b, one possible mannerin which the “first”, or “base”, header unit (a header unit 110, in thecase of these illustrative Figures) is provided for, positioned, andconnected to the foundation element is shown. Particularly, thefoundation element 1450, 500 is cast under and around a suspended headerform 1410 which is shaped such that it is compliant with the base headerunit 110, which is the first unit in the assembly of the header stack101, but is dimensioned slightly larger, sufficient to facilitate thecorrect flow and placement of the adhesive/filler grout forming andfacilitating the correct connection between header unit 110 andfoundation element 1450, 500. The header forms 1410 are preferablyconstructed from a high strength material, resilient and abrasionresistant, such as polypropylene, which material may be augmentedinternally with a strengthening and/or stiffening frame. The headerforms 1410 also serve to situate the passthrough tendons, or activereinforcement elements 115 in place for formation of the foundationelement 1450, 500. Where longitudinal passive reinforcement elements 115p are being installed in conjunction with the header stack 101, theheader forms 1410 also will situate such reinforcement elements 115 p.The foundation element 1450, 500 is cast under and around the forms 1410and when the foundation element 1450 cures sufficiently, the headerforms 1410 are removed, leaving a recess pattern 1420 in which toplace/suspend the header units 110. The header units 110 are placed inthe recess pattern 1420, leaving an annular space 1422 around andbeneath the header unit 110. The annular space is best seen in FIG. 14b. The annular space 1422 is then filled with a grout or epoxy (notshown) which holds the header unit 110 in place, and provides theappropriate connection between the header unit 110 and the foundationelement 1450, 500. The header units 110 must be situated on thefoundation element 1450, 500, such that they are as close to perfectlyhorizontal as possible as they are the header units on which the headerstacks and, hence, the entire construction 800 is built. In particular,the parallel top and bottom flat surfaces of this “base” header unit 110must be horizontal as defined by and with respect to the direction whichis both perpendicular to the front-to-back axis of the header unit 110and perpendicular to the longitudinal axis of the header stack beingconstructed. Alternatively, the normal to the parallel top and bottomflat surfaces of the “base” header unit 110 must be parallel to the axisof the header stack being assembled, whose axis must be in a verticalplane and which vertical plane is perpendicular to the plan curve ofconstruction of the retaining wall, which curve may be a straight line.A very small deviation from this particular requirement would beunacceptable because the deviation would be grossly amplified in aheader stack 101 of any significant height. Specifically designed andmanufactured construction temporary support equipment 1500 is used toposition and then secure the header unit 110 in place while the grout,or other connecting agent, cures. Where header stack construction isbeing continued on and above a complementary structural element 1100, anidentical or similar procedure may be followed for the preparation forand positioning of the “first” or “base” header unit on and theconnection to such complementary element 1100. Further, such headerforms may be used to locate the passthrough ducts that are employed inconjunction with any active reinforcement elements 115 and/or passivereinforcement elements 115 p as are structurally associated with theheader stack 101. This process, specifically employing a header form,which is aimed at the correct and rapid set-up of the first or baseheader unit on a foundation element 1450, 500, or complementarystructural element 1100, comprises an essentially identical alternativefor each of the various header types 110, 2700 which comprise thecollection of header units of the present invention.

The placing of the “first” or “base” header units 110 on the foundationelement 1450, 500 may also be accomplished without the header forms1410. In such a situation, construction equipment 1480 (see, forexample, FIGS. 15 a and 15 b) would be utilized to hold a header unit110 in a correct location, possessing correct spatial orientation,suspended above the reinforcement 1458 of the foundation element 1450,500 and the foundation 1450 concrete would be cast beneath and aroundit. That is, as determined by the project design, the cast-in-placeconcrete of the foundation element 1450, 500, may encroach up the wallsof the first, or base, header unit 110 for various job-specific reasons.Again, little tolerance for error is allowed, the header unit 110 mustbe horizontal. In particular, the parallel top and bottom flat surfacesof this “base” header unit 110 must be horizontal as defined by and withrespect to the direction which is both perpendicular to thefront-to-back axis of the header unit 110 and perpendicular to thelongitudinal axis of the header stack being constructed. Alternatively,the normal to the parallel top and bottom flat surfaces of the “base”header unit 110 must be parallel to the axis of the header stack beingassembled, whose axis must be in a vertical plane and which verticalplane is perpendicular to the plan curve of construction of theretaining wall, which curve may be a straight line. Because of thesepositioning requirements the construction equipment 1480, 1500 issufficiently robust and both capable of fine adjustment and ofmaintaining such positional settings during the full process andactivities of construction to which such equipment will be subjected.Either method for positioning the first or base header unit 110 on thefoundation element 1450, 500 can also be used in positioning the firstor base header units 110 on the tieback transfer beams 1100, or othertype of complementary structural element 1100. This process,specifically suspending a header unit 110, which is aimed at the correctand rapid set-up of the first or base header unit on a foundationelement 1450, 500, or complementary structural element 1100, comprisesan essentially identical alternative for each of the various headertypes 110, 2700 which comprise the collection of header units of thepresent invention. A plurality of header stacks 101 are constructed onthe foundation element 1450, 500 with each header stack 101, 2701comprising a plurality of header units 110, 2700. The header units 110,2700 are those previously described. An active reinforcement element 115is coupled to each header stack 2701, 101 and is post-tensioned suchthat it imparts a corresponding pre-stressing force into the headerstack 2701, 101. A passive reinforcement element 115 p may be providedwithin and through the passthrough ducts of the header units tostructurally work in conjunction with the active reinforcement elements115, which passive reinforcement elements 115 p augment the structuralperformance contribution of active reinforcement elements 115. Suchpassive reinforcement element 115 p, where included within the headerstack construction, is made to work in conjunction with the header stackvia bond, which bond is provided via the grouting of the space about thepassive reinforcement element 115 p and within the passthrough ducthousing such element 115 p.

The construction of the header stacks 2701, 101 comprises stacking aplurality of header units 2700, 110 on the foundation element 1450, 500.It is desired to pre-position the active reinforcement element 115 inthe foundation element 1450, 500. In such a configuration, the headerunits 2700, 110 are then fed over the active reinforcement elements 115,the active reinforcement element 115 passing through a passthrough duct116, 2716. The active reinforcement element 115 is then secured to theheader stack 2701, 101 as previously described. In an embodiment of theinvention, a harping element 1910 is coupled to the header stack at aharping point 1905 such that the active reinforcement element 115 isdisposed external to the header stack 101 and is redirected at theharping point 1905 such that the active reinforcement element 115 formsa series of substantially straight segments 1901, 1902, 1903.

Note that any of the header units 2700, 110 described above can beutilized with the method of construction of the present invention.

To describe some possible applications and to express the flexibility ofthe system of the present invention, the following examples are given.It is to be understood that the details in the examples are simplifiedto describe the primary factors involved in such modular constructionsas described. As would be apparent to one of ordinary skill in the art,other factors may affect the design considerations. These examplesshould not represent any limitation on the present invention.Corresponding reference numerals will be used where appropriate.

Referring to FIGS. 34 c, 34 d, and 34 e, the flexibility of the systemsof the present invention is depicted. FIG. 34 c depicts a structure 3490being support by a retaining wall 800 which incorporates header stacks2701, and a complementary structural element 1100. The structure 3490 inFIG. 34 c is configured to protect the roadway 3500 below from fallingdebris. There is a shield 3495 which protects the primary shield orstructure 3490. Note that the roadway is supported by a structure suchas those described with reference to FIG. 34 b. The structure 3490 inFIG. 34 e is an elevated roadway that could be constructed in highlycongested areas. Element 3495′ in FIG. 34 e is a support structure forthe elevated roadway 3490.

The structure 3510 depicted in FIG. 34 d is suspended primarily throughthe use of complementary structural elements 1100. Such a structureillustrates the vast range of uses of the system of the presentinvention.

Referring to FIGS. 34 g and 34 h, and FIGS. 34 m and 34 n, anotherapplication of the systems of the present invention is shown. The needto simultaneously provide support for the ends of a bridge and to retainthe soil mass at those locations is a common problem in highwayengineering. The structure that provides for these requirements iscommonly known as a bridge abutment 3401. Specifically, the abutment3401 transmits the reactions from the bridge superstructure (e.g.,girders) 3402 to the foundation system 3410 and, secondly, retains thesoils comprising the earth embankment of the approach roadway.

The different restrictions and requirements that can occur at theseabutment locations are numerous. However, the systems of the presentinvention provide a wide array of options, from which the designengineer may choose, in developing a competent solution meeting thedemands of any given bridge site.

The situation that is addressed in FIGS. 34 g, 34 h, 34 m and 34 n isone where a new freeway system is being pushed through an area that alsodemands overpass bridges to serve local transportation needs. It hasbeen determined, because of the local peculiarities of the area, thatthe freeway may be constructed at reduced elevation, with a series ofsimple overpass bridges. Further, because of restricted right-of-way,the design calls for vertical retaining walls on either side of thefreeway. This example demonstrates the use of the embodiment of theheader units 110 described above and depicted in FIGS. 1-5 and FIGS. 22and 23 in the construction of the necessary retention and supportstructure.

What is further demonstrated, is the ready inclusion of the overpassbridge abutment. The construction of the bottom slab and the end returnwalls of the abutment is aided by the use of the same equipment used forthe construction of Tieback Transfer Beams (TTBs) and capping beams,which also are used on either side of this abutment.

FIG. 34 g shows a general overview of an included abutment 3401. FIG. 34h shows a close-up of the abutment 3401 structure seated on the modularconstruction of the present invention, with some of the overpasssteel-plate girders 3402 being lifted into position. FIGS. 34 m and 34 nshow a construction similar to that in FIGS. 34 g and 34 h, but includean alternative embodiment of the header stacks of the present invention.

FIG. 34 a depicts the potential use of the systems of the presentinvention to support large cantilever structures 3450. The modularconstruction 800 is constructed using header units 2700 to form a headerstack 2701 to retain a soil load 34. The system also incorporates acomplementary structural element 1100 and a ground anchor 1115 toprovide additional capability and stability to the system.

Turning now to FIGS. 34 b and 34 f, the use of the systems to combatcliff erosion is depicted in another application of the system of thepresent invention. Thousands of communities worldwide, both large andsmall, are located on a shoreline. Frequently, having been establishedover long periods, these communities now find themselves being severelyencroached upon by the action of the eroding environmental elements.

As is common along part of the California coastline near Santa Cruz,which comprises the general location of the bluff face considered inthis example, the base of the cliff is composed of a reasonablycompetent sedimentary rock. In this location, purisima is the geologicalname given this sedimentary rock. The soils overlaying the purisimarock, the terrace deposits, are more or less consistent and comprisegenerally weak, unconsolidated conglomerates. Because of the soilcharacteristics and the particle grading of these conglomerates, theyfrequently stand at very steep angles, sometimes forming over-verticalfaces. However, these terrace deposits continuously erode, often in aseries of non-rotational slip failures, with most erosion activityoccurring towards the end of the winter period.

A second and independent form of cliff erosion occurs when failure isinduced in the purisima sedimentary rock. This type of failure is causedby the undermining of the relatively soft rock. The natural attrition ofthis soft rock at the base is caused principally by the flittering ofthe purisima, which in turn is caused by the general eroding action ofthe elements, including wave action. Eventually the underminingprogresses to such an extent it causes the sedimentary rock to fall outin slabs and/or blocks, depending on preexisting fracture planes.Ultimately, though sometimes directly, this leaves the conglomeratesabove unsupported and triggers a consequent failure in the terracedeposits.

In this location, as in many others, there is a public roadway that,when originally constructed, was some distance from the cliff edge.Because of the erosion over the years, the roadway was reduced from twolanes to a single lane. In several places the guard rails were hangingin mid-air. In many other places the roadways are cut completely. Itshould be noted that the loss of some of the roads and, in manylocations, the loss of private property, was caused by earthquakeinduced rock/soil-mass failures.

There are several ways to combat these types of soil retention andprotection problems. The systems of the present invention offer numerouspossible solutions.

The design depicted in FIG. 34 b addresses several issues. Ultimately,these issues amount to dealing with the time and cost of constructionwhile providing the solution functionality and performance required.

In particular, the solution employs pre-cast cantilever units that thesesystems naturally incorporate into the structure. The system of thepresent invention can include large cantilever units (for example, asdepicted in FIG. 34 a) at very low additional expense (especially whencompared to the added functionality acquired), that can regain“property” lost to the effects of erosion. In this situation, this addedarea can be utilized as vehicular parking, wider pedestrian pathways,bike and roller-blading lanes, and/or lookouts.

What is also significant with the use of cantilever units in general, asattached to the top of the retaining wall, is the freedom of position itaffords with regard to the location of the foundation elements. Theseand other pre-cast concrete elements (as well as structural componentsmade from steel), may be included and/or attached to the retaining wallstructure at levels other than the top of the header stacks. In theparticular situation depicted in FIG. 34 b, the pre-cast concretecantilever units allow the construction of the foundation element to belocated at the interface of the purisima sedimentary rock and theterrace deposits.

Locating the foundation construction at this interface provides severaladvantages:

-   -   The construction contractor does not need to commence work at        the base of the cliff where there is much greater exposure to        the whims of the ocean. The typical issue of foundations being        inundated with seawater, and the associated problems, are        immediately eliminated.    -   The depth from the top of finished construction to the        foundation beam/pile cap is significantly less than the height        of the cliff, and access may be readily established from the        roadway above.    -   Because of the competency of the sedimentary rock, the piles may        be installed most rapidly, typically not requiring any shoring,        and thus allowing for the optimized use of the drilling rigs. In        the few locations where the rock cover is insufficient to        contain the bursting pressures generated by the compaction of        the wet concrete, the upper few feet of the pile may be sleeved.    -   Ground anchors are installed under optimum conditions.    -   The foundation beam/pile cap is then readily placed to the        accuracy required by the system for the first layer of header        units, and the placing of remaining pre-cast modules may proceed        with rapidity.    -   The pre-cast cantilever units are installed and, having already        developed ample strength, may immediately carry the loads of the        forms, rebar and concrete necessary to complete the structure.

One of the most significant savings established by the approach that canbe taken with these systems is the elimination of wall construction overthe height of the exposed purisima sedimentary rock.

FIGS. 34 i and 34 j illustrate the use of headers 2700 in conjunctionwith cast-in-place (CIP) concrete panels 130 c. The CIP panels 130 c inthe illustration are formed with simple patterned front faces. The facesof the panels 130 c can be patterned in various ways to meet therequirements of the owner. The use of complementary structural element1100 along with the restraining ground anchor 1115 forces which apply atthe complementary structural elements 1100, provide for efficient use ofthe header stacks 2701 in conjunction with the CIP panels 130 c becauseof the composite action which may develop between these components. FIG.34 j depicts the rear face of the wall shown in FIG. 34 i.

FIGS. 34 k and 34 l further illustrate the flexibility of the systems ofthe present invention. In a situation where a sloped construction isrequired, the header stacks 101 are stepped and the capping beam 3409 isformed to abut the adjacent header unit 110. The cast-in-place concretepanels 130 c are formed to substantially fill the area between theheader stacks 101. The complementary structural element 1100 depicted inthe figure is physically close to the capping beam 3409 due to the steepslope of the capping beam 3409. Note that the complementary structuralelements 1100 for any construction may step at various intervals withouthaving to be continuous across the entire length of the wall 800.

FIGS. 34 o, 34 p, 34 q illustrate a situation where there is significantrock formation obstructing the path of where a construction is desired.The rock formation may be too costly to remove or may need to be left inplace for various other reasons. In such a situation, the modularconstructions of the present invention may be configured to provide asuperior solution, readily overcoming such obstacles. Note that theelement that serves as a complementary structural element 1100 at thesection of the wall depicted in FIG. 34 q serves as the foundationelement 500 for the section of the wall depicted in FIG. 34 p. Togetherwith complementary structural elements 1100, the appropriate location,spacing, capacity, and declination of ground anchors 1115 provides agreat scope of application and flexibility of the systems of the presentinvention.

The potential use of ground anchors 1115 is further illustrated in FIG.34 r. In this example an elevated railroad line built on a levelcrossing is depicted. The system incorporates cantilever units at thetop of opposing retaining walls. Very large lateral forces may developduring and after construction, which forces will act on the retainingwall structure 800. A system from the present invention maybe chosenwith the capacity to withstand these lateral forces (and the resultantmoments and shears, etc.) in a strictly cantilever action. Anotheroption that significantly reduces, or may eliminate, the moments and theshear forces “seen” by the foundation element 500 at the base of suchwall construction, is afforded via the use of incorporated complementarystructural elements 1100, which elements 1100 may then be “tiedtogether” via horizontal ground anchors 1115, or similar ties 1115. Notethat such ties 1115 are also employed as shown between the foundationelements 500 themselves.

CONCLUSION

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. Thus, the breadth and scope of thepresent invention should not be limited by any of the above-describedexemplary embodiments, but should be defined only in accordance with thefollowing claims and their equivalents.

1.-73. (canceled)
 74. An apparatus, comprising: a header configured to be stacked with an adjacent header to form a load-bearing structure, the header including an upper surface, a lower surface, and a side surface, the upper surface of the header configured to be in contact with a lower surface of the adjacent header, the upper surface of the header defining an opening configured to receive a protrusion of the lower surface of the adjacent header when the header is stacked with the adjacent header such that the side surface of the header and a side surface of the adjacent header form a substantially continuous surface, the header defining a lumen therethrough configured to receive an active reinforcement element, the active reinforcement element configured to impart a pre-stressing force associated with the header.
 75. The apparatus of claim 74, wherein: the upper surface of the header is substantially planar; and the lower surface of the header is substantially planar and parallel to the upper surface of the header.
 76. The apparatus of claim 74, wherein: the opening is a first opening; and the upper surface of the header defines a second opening, the second opening in communication with the lumen, the second opening configured to receive a lock-off element.
 77. The apparatus of claim 74, wherein: the opening is a first opening; and the upper surface of the header defines a second opening, the second opening in communication with the lumen, the second opening having a non-circular shape, the second opening configured to receive a lock-off element such that a surface of the lock-off element is flush with the upper surface of the header.
 78. The apparatus of claim 74, wherein the header is configured to be coupled to a secondary structural member such that the header, the adjacent header, and the secondary structural member collectively form at least a portion of a retaining wall.
 79. The apparatus of claim 74, wherein: the lumen is a first lumen, a longitudinal axis of the first lumen being substantially normal to the upper surface of the header; and the header defines a second lumen configured to receive a passive reinforcement element, a longitudinal axis of the second lumen being substantially parallel to the upper surface of the header.
 80. The apparatus of claim 74, wherein the side surface of the header and the side surface of the adjacent header form a substantially coplanar surface when the header is stacked with the adjacent header and when the opening of the first surface of the header receives the protrusion of the lower surface of the adjacent header.
 81. The apparatus of claim 74, wherein: the adjacent header is a first adjacent header; and the lower surface of the header includes a protrusion configured to be disposed within an opening of an upper surface of a second adjacent header.
 82. The apparatus of claim 74, further comprising the active reinforcement element.
 83. The apparatus of claim 74, further comprising the active reinforcement element, the active reinforcement element being bonded within the lumen.
 84. An apparatus, comprising: a header configured to be stacked with an adjacent header to form a load-bearing structure, the header including a first end portion, a second end portion, and a central portion disposed between the first end portion and the second end portion, an upper surface of the central portion including a corrugated portion configured to matingly fit with a corrugated portion of a lower surface of the adjacent header when the header is stacked with the adjacent header such that a side surface of the central portion of the header and a side surface of the adjacent header are substantially aligned, the first end portion of the header defining a lumen therethrough configured to receive a reinforcement element.
 85. The apparatus of claim 84, wherein: the lumen of the first end portion is configured to receive an active reinforcement element configured to impart a pre-stressing force associated with the header.
 86. The apparatus of claim 84, wherein: the opening is a first opening; the lumen of the first end portion is configured to receive an active reinforcement element configured to impart a pre-stressing force associated with the header; and a surface of the first end portion of the header defines a second opening, the second opening in communication with the lumen, the second opening configured to receive a lock-off element, the lock-off element configured to engage the active reinforcement element to maintain a post-tensioning force applied to the active reinforcement element.
 87. The apparatus of claim 84, wherein the lumen of the first end portion includes a conduit therein, the conduit configured to prevent the reinforcement element from being bonded directly to the header within the lumen.
 88. The apparatus of claim 84, wherein: a width of the first end portion of the header is substantially equal to a width of the second end portion of the header; and a width of the central portion of the header is less than the width of the first end portion of the header.
 89. The apparatus of claim 84, wherein the header is configured to be coupled to a secondary structural member such that the header, the adjacent header, and the secondary structural member collectively form at least a portion of a retaining wall.
 90. The apparatus of claim 84, wherein the side surface of the central portion of the header and the side surface of the adjacent header form a substantially coplanar surface when the header is stacked with the adjacent header and when the corrugated portion of the upper surface of the central portion is matingly fit with the corrugated portion of the lower surface of the adjacent header.
 91. An apparatus, comprising: a header configured to be stacked with an adjacent header to form a load-bearing structure, the header including a first end portion, a second end portion, and a central portion disposed between the first end portion and the second end portion, a width of the first end portion of the header being substantially equal to a width of the second end portion of the header, a width of the central portion of the header being less than the width of the first end portion of the header, the header defining a lumen therethrough configured to receive an active reinforcement element, the active reinforcement element configured to impart a pre-stressing force associated with the header.
 92. The apparatus of claim 91, wherein: an upper surface of the central portion defines an opening configured to receive a protrusion of the lower surface of a central portion of the adjacent header when the header is stacked with the adjacent header.
 93. The apparatus of claim 91, wherein: a height of the first end portion of the header is substantially equal to a height of the second end portion of the header; and the height of the first end portion of the header is substantially equal to a height of the central portion of the header.
 94. The apparatus of claim 91, wherein: the opening is a first opening; and a surface of the first end portion of the header defines a second opening, the second opening in communication with the lumen, the second opening configured to receive a lock-off element, the lock-off element configured to engage the active reinforcement element to maintain a post-tensioning force applied to the active reinforcement element. 